diff --git a/common/rpc-service.c b/common/rpc-service.c
index 6c0b20b4..32a7503c 100644
--- a/common/rpc-service.c
+++ b/common/rpc-service.c
@@ -988,3 +988,9 @@ seafile_sync_error_id_to_str (int error_id, GError **error)
 {
     return g_strdup(sync_error_id_to_str (error_id));
 }
+
+int
+seafile_add_del_confirmation (const char *confirmation_id, int resync, GError **error)
+{
+    return seaf_sync_manager_add_del_confirmation (seaf->sync_mgr, confirmation_id, resync);
+}
diff --git a/daemon/seaf-daemon.c b/daemon/seaf-daemon.c
index 07794cd0..591c0bac 100644
--- a/daemon/seaf-daemon.c
+++ b/daemon/seaf-daemon.c
@@ -92,6 +92,11 @@ register_rpc_service ()
                                      "seafile_sync_error_id_to_str",
                                      searpc_signature_string__int());
 
+    searpc_server_register_function ("seafile-rpcserver",
+                                     seafile_add_del_confirmation,
+                                     "seafile_add_del_confirmation",
+                                     searpc_signature_int__string_int());
+
     searpc_server_register_function ("seafile-rpcserver",
                                      seafile_get_config,
                                      "seafile_get_config",
diff --git a/daemon/seafile-config.c b/daemon/seafile-config.c
index 5d721fa3..518b1037 100644
--- a/daemon/seafile-config.c
+++ b/daemon/seafile-config.c
@@ -168,6 +168,9 @@ seafile_session_config_set_int (SeafileSession *session,
     if (g_strcmp0(key, KEY_PROXY_PORT) == 0) {
         session->http_proxy_port = value;
     }
+    if (g_strcmp0(key, KEY_DELETE_CONFIRM_THRESHOLD) == 0) {
+        session->delete_confirm_threshold = value;
+    }
 
     return 0;
 }
diff --git a/daemon/seafile-config.h b/daemon/seafile-config.h
index e81881b5..772e171d 100644
--- a/daemon/seafile-config.h
+++ b/daemon/seafile-config.h
@@ -37,6 +37,7 @@
 #define KEY_PROXY_PASSWORD "proxy_password"
 #define PROXY_TYPE_HTTP "http"
 #define PROXY_TYPE_SOCKS "socks"
+#define KEY_DELETE_CONFIRM_THRESHOLD "delete_confirm_threshold"
 
 gboolean
 seafile_session_config_exists (SeafileSession *session, const char *key);
diff --git a/daemon/seafile-error.c b/daemon/seafile-error.c
index 0c43f1f1..b63448e7 100644
--- a/daemon/seafile-error.c
+++ b/daemon/seafile-error.c
@@ -174,6 +174,11 @@ static SyncErrorInfo sync_error_info_tbl[] = {
         SYNC_ERROR_LEVEL_REPO,
         "Library is too large to sync"
     },
+    {
+        SYNC_ERROR_ID_DEL_CONFIRMATION_PENDING,
+        SYNC_ERROR_LEVEL_REPO,
+        "Waiting for confirmation to delete files"
+    },
 };
 
 const char *
diff --git a/daemon/seafile-session.c b/daemon/seafile-session.c
index a2f28b59..2461b5f4 100644
--- a/daemon/seafile-session.c
+++ b/daemon/seafile-session.c
@@ -348,6 +348,8 @@ out:
     g_key_file_free (key_file);
 }
 
+#define MAX_DELETED_FILES_NUM 500
+
 void
 seafile_session_prepare (SeafileSession *session)
 {
@@ -415,6 +417,10 @@ seafile_session_prepare (SeafileSession *session)
             seafile_session_config_get_string(session, KEY_PROXY_PASSWORD);
     }
 
+    session->delete_confirm_threshold = seafile_session_config_get_int (session, KEY_DELETE_CONFIRM_THRESHOLD, NULL);
+    if (session->delete_confirm_threshold <= 0)
+        session->delete_confirm_threshold = MAX_DELETED_FILES_NUM;
+
     int block_size = seafile_session_config_get_int(session, KEY_CDC_AVERAGE_BLOCK_SIZE, NULL);
     if (block_size >= 1024) {
         session->cdc_average_block_size = block_size;
diff --git a/daemon/seafile-session.h b/daemon/seafile-session.h
index 30ad841e..89a4d370 100644
--- a/daemon/seafile-session.h
+++ b/daemon/seafile-session.h
@@ -88,6 +88,7 @@ struct _SeafileSession {
     int                  http_proxy_port;
     char                *http_proxy_username;
     char                *http_proxy_password;
+    int                 delete_confirm_threshold;
 };
 
 struct _SeafileSessionClass
diff --git a/daemon/sync-mgr.c b/daemon/sync-mgr.c
index e54818c4..6489b91c 100644
--- a/daemon/sync-mgr.c
+++ b/daemon/sync-mgr.c
@@ -15,6 +15,7 @@
 #include "vc-utils.h"
 
 #include "sync-status-tree.h"
+#include "diff-simple.h"
 
 #ifdef WIN32
 #include <shlobj.h>
@@ -62,6 +63,10 @@ struct _HttpServerState {
 };
 typedef struct _HttpServerState HttpServerState;
 
+typedef struct DelConfirmationResult {
+    gboolean resync;
+} DelConfirmationResult;
+
 struct _SeafSyncManagerPriv {
     struct SeafTimer *check_sync_timer;
     struct SeafTimer *update_tx_state_timer;
@@ -77,6 +82,9 @@ struct _SeafSyncManagerPriv {
     GAsyncQueue *refresh_paths;
     struct SeafTimer *refresh_windows_timer;
 #endif
+
+    pthread_mutex_t del_confirmation_lock;
+    GHashTable *del_confirmation_tasks;
 };
 
 struct _ActivePathsInfo {
@@ -165,6 +173,11 @@ seaf_sync_manager_new (SeafileSession *seaf)
     mgr->priv->refresh_paths = g_async_queue_new ();
 #endif
 
+    mgr->priv->del_confirmation_tasks = g_hash_table_new_full (g_str_hash, g_str_equal,
+                                                           g_free,
+                                                           g_free);
+    pthread_mutex_init (&mgr->priv->del_confirmation_lock, NULL);
+
     return mgr;
 }
 
@@ -970,6 +983,11 @@ commit_job (void *vtask)
     return res;
 }
 
+static char *
+exceed_max_deleted_files (SeafRepo *repo);
+static void
+notify_delete_confirmation (const char *repo_name, const char *desc, const char *confirmation_id);
+
 static void
 commit_job_done (void *vres)
 {
@@ -998,8 +1016,20 @@ commit_job_done (void *vres)
         return;
     }
 
-    if (res->changed)
+    if (res->changed) {
+        char *desc = NULL;
+        desc = exceed_max_deleted_files (repo);
+        if (desc) {
+            notify_delete_confirmation (repo->name, desc, repo->head->commit_id);
+            seaf_warning ("Delete more than %d files, add delete confirmation.\n", seaf->delete_confirm_threshold);
+            task->info->del_confirmation_pending = TRUE;
+            set_task_error (res->task, SYNC_ERROR_ID_DEL_CONFIRMATION_PENDING);
+            g_free (desc);
+            g_free (res);
+            return;
+        }
         start_upload_if_necessary (res->task);
+    }
     else if (task->is_manual_sync || task->is_initial_commit)
         check_head_commit_http (task);
     else
@@ -1186,6 +1216,194 @@ out:
     return ret;
 }
 
+#define MAX_DELETED_FILES_NUM 100
+
+inline static char *
+get_basename (char *path)
+{
+    char *slash;
+    slash = strrchr (path, '/');
+    if (!slash)
+        return path;
+    return (slash + 1);
+}
+
+static char *
+exceed_max_deleted_files (SeafRepo *repo)
+{
+    SeafBranch *master = NULL, *local = NULL;
+    SeafCommit *local_head = NULL, *master_head = NULL;
+    GList *diff_results = NULL;
+    char *deleted_file = NULL;
+    GString *desc = NULL;
+    char *ret = NULL;
+
+    local = seaf_branch_manager_get_branch (seaf->branch_mgr, repo->id, "local");
+    if (!local) {
+        seaf_warning ("No local branch found for repo %s(%.8s).\n",
+                      repo->name, repo->id);
+        goto out;
+    }
+
+    master = seaf_branch_manager_get_branch (seaf->branch_mgr, repo->id, "master");
+    if (!master) {
+        seaf_warning ("No master branch found for repo %s(%.8s).\n",
+                      repo->name, repo->id);
+        goto out;
+    }
+
+    local_head = seaf_commit_manager_get_commit (seaf->commit_mgr, repo->id, repo->version,
+                                                 local->commit_id);
+    if (!local_head) {
+        seaf_warning ("Failed to get head of local branch for repo %s.\n", repo->id);
+        goto out;
+    }
+
+    master_head = seaf_commit_manager_get_commit (seaf->commit_mgr, repo->id, repo->version,
+                                                  master->commit_id);
+    if (!master_head) {
+        seaf_warning ("Failed to get head of master branch for repo %s.\n", repo->id);
+        goto out;
+    }
+
+    diff_commit_roots (repo->id, repo->version, master_head->root_id, local_head->root_id, &diff_results, TRUE);
+    if (!diff_results) {
+        goto out;
+    }
+    GList *p;
+    DiffEntry *de;
+    int n_deleted = 0;
+
+    for (p = diff_results; p != NULL; p = p->next) {
+        de = p->data;
+        switch (de->status) {
+        case DIFF_STATUS_DELETED:
+            if (n_deleted == 0)
+                deleted_file = get_basename(de->name);
+            n_deleted++;
+            break;
+        }
+    }
+
+    if (n_deleted >= seaf->delete_confirm_threshold) {
+        desc = g_string_new ("");
+        g_string_append_printf (desc, "Deleted \"%s\" and %d more files.\n",
+                                deleted_file, n_deleted - 1);
+        ret = g_string_free (desc, FALSE);
+    }
+
+out:
+    seaf_branch_unref (local);
+    seaf_branch_unref (master);
+    seaf_commit_unref (local_head);
+    seaf_commit_unref (master_head);
+    g_list_free_full (diff_results, (GDestroyNotify)diff_entry_free);
+
+    return ret;
+}
+
+static void
+notify_delete_confirmation (const char *repo_name, const char *desc, const char *confirmation_id)
+{
+    json_t *obj = json_object ();
+    json_object_set_string_member (obj, "repo_name", repo_name);
+    json_object_set_string_member (obj, "delete_files", desc);
+    json_object_set_string_member (obj, "confirmation_id", confirmation_id);
+
+    char *msg = json_dumps (obj, JSON_COMPACT);
+
+    seaf_mq_manager_publish_notification (seaf->mq_mgr, "sync.del_confirmation", msg);
+
+    json_decref (obj);
+    g_free (msg);
+}
+
+int
+seaf_sync_manager_add_del_confirmation (SeafSyncManager *mgr,
+                                        const char *confirmation_id,
+                                        gboolean resync)
+{
+    SeafSyncManagerPriv *priv = seaf->sync_mgr->priv;
+    DelConfirmationResult *result = NULL;
+
+    result = g_new0 (DelConfirmationResult, 1);
+    result->resync = resync;
+
+    pthread_mutex_lock (&priv->del_confirmation_lock);
+    g_hash_table_insert (priv->del_confirmation_tasks, g_strdup (confirmation_id), result);
+    pthread_mutex_unlock (&priv->del_confirmation_lock);
+
+    return 0;
+}
+
+static DelConfirmationResult *
+get_del_confirmation_result (const char *confirmation_id)
+{
+    SeafSyncManagerPriv *priv = seaf->sync_mgr->priv;
+    DelConfirmationResult *result, *copy = NULL;
+
+
+    pthread_mutex_lock (&priv->del_confirmation_lock);
+    result = g_hash_table_lookup (priv->del_confirmation_tasks, confirmation_id);
+    if (result) {
+        copy = g_new0 (DelConfirmationResult, 1);
+        copy->resync = result->resync;
+        g_hash_table_remove (priv->del_confirmation_tasks, confirmation_id);
+    }
+    pthread_mutex_unlock (&priv->del_confirmation_lock);
+
+    return copy;
+}
+
+static void
+resync_repo (SeafRepo *repo)
+{
+    GError *error = NULL;
+    char *repo_id = g_strdup (repo->id);
+    int repo_version = repo->version;
+    char *repo_name = g_strdup (repo->name);
+    char *token = g_strdup (repo->token);
+    char *magic = g_strdup (repo->magic);
+    int enc_version = repo->enc_version;
+    char *random_key = g_strdup (repo->random_key);
+    char *worktree = g_strdup (repo->worktree);
+    char *email = g_strdup (repo->email);
+    char *more_info = NULL;
+    json_t *obj = json_object ();
+
+    json_object_set_int_member (obj, "is_readonly", repo->is_readonly);
+    json_object_set_string_member (obj, "repo_salt", repo->salt);
+    json_object_set_string_member (obj, "server_url", repo->server_url);
+
+    more_info = json_dumps (obj, 0);
+
+    if (repo->auto_sync && (repo->sync_interval == 0))
+        seaf_wt_monitor_unwatch_repo (seaf->wt_monitor, repo->id);
+
+    seaf_repo_manager_del_repo (seaf->repo_mgr, repo);
+
+    char *ret = seaf_clone_manager_add_task (seaf->clone_mgr, repo_id,
+                                             repo_version, repo_name,
+                                             token, NULL,
+                                             magic, enc_version,
+                                             random_key, worktree,
+                                             email, more_info, &error);
+    if (error) {
+        seaf_warning ("Failed to clone repo %s: %s\n", repo_id, error->message);
+        g_clear_error (&error);
+    }
+    g_free (ret);
+    g_free (repo_id);
+    g_free (repo_name);
+    g_free (token);
+    g_free (magic);
+    g_free (random_key);
+    g_free (worktree);
+    g_free (email);
+    json_decref (obj);
+    g_free (more_info);
+}
+
 static int
 sync_repo_v2 (SeafSyncManager *manager, SeafRepo *repo, gboolean is_manual_sync)
 {
@@ -1224,6 +1442,36 @@ sync_repo_v2 (SeafSyncManager *manager, SeafRepo *repo, gboolean is_manual_sync)
     if (strcmp (master->commit_id, local->commit_id) != 0) {
         if (is_manual_sync || can_schedule_repo (manager, repo)) {
             task = create_sync_task_v2 (manager, repo, is_manual_sync, FALSE);
+            if (!task->info->del_confirmation_pending) {
+                char *desc = NULL;
+                desc = exceed_max_deleted_files (repo);
+                if (desc) {
+                    notify_delete_confirmation (repo->name, desc, local->commit_id);
+                    seaf_warning ("Delete more than %d files, add delete confirmation.\n", seaf->delete_confirm_threshold);
+                    task->info->del_confirmation_pending = TRUE;
+                    set_task_error (task, SYNC_ERROR_ID_DEL_CONFIRMATION_PENDING);
+                    g_free (desc);
+                    goto out;
+                }
+            } else {
+                DelConfirmationResult *result = get_del_confirmation_result (local->commit_id);
+                if (!result) {
+                    // User has not confirmed whether to continue syncing.
+                    set_task_error (task, SYNC_ERROR_ID_DEL_CONFIRMATION_PENDING);
+                    goto out;
+                } else if (result->resync) {
+                    // User chooses to resync.
+                    g_free (result);
+                    task->info->del_confirmation_pending = FALSE;
+                    set_task_error (task, SYNC_ERROR_ID_DEL_CONFIRMATION_PENDING);
+                    // Delete this repo and resync this repo by adding clone task.
+                    resync_repo (repo);
+                    goto out;
+                }
+                // User chooes to continue syncing.
+                g_free (result);
+                task->info->del_confirmation_pending = FALSE;
+            }
             start_upload_if_necessary (task);
         }
         /* Do nothing if the client still has something to upload
diff --git a/daemon/sync-mgr.h b/daemon/sync-mgr.h
index dbc564d3..c5a4786a 100644
--- a/daemon/sync-mgr.h
+++ b/daemon/sync-mgr.h
@@ -35,6 +35,7 @@ struct _SyncInfo {
     gboolean   end_multipart_upload;
 
     gint       sync_perm_err_cnt;
+    gboolean   del_confirmation_pending;
 };
 
 enum {
@@ -129,6 +130,11 @@ SyncInfo *
 seaf_sync_manager_get_sync_info (SeafSyncManager *mgr,
                                  const char *repo_id);
 
+int
+seaf_sync_manager_add_del_confirmation (SeafSyncManager *mgr,
+                                        const char *confirmation_id,
+                                        gboolean resync);
+
 int
 seaf_sync_manager_disable_auto_sync (SeafSyncManager *mgr);
 
diff --git a/include/seafile-error.h b/include/seafile-error.h
index b115eca7..b794f0d4 100644
--- a/include/seafile-error.h
+++ b/include/seafile-error.h
@@ -62,6 +62,7 @@
 #define SYNC_ERROR_ID_REMOVE_UNCOMMITTED_FOLDER 30
 #define SYNC_ERROR_ID_INVALID_PATH_ON_WINDOWS   31
 #define SYNC_ERROR_ID_LIBRARY_TOO_LARGE         32
-#define N_SYNC_ERROR_ID                         33
+#define SYNC_ERROR_ID_DEL_CONFIRMATION_PENDING  33
+#define N_SYNC_ERROR_ID                         34
 
 #endif
diff --git a/include/seafile-rpc.h b/include/seafile-rpc.h
index 36d22f68..518fe3aa 100644
--- a/include/seafile-rpc.h
+++ b/include/seafile-rpc.h
@@ -216,4 +216,7 @@ seafile_shutdown (GError **error);
 
 char*
 seafile_sync_error_id_to_str (int error_id, GError **error);
+
+int
+seafile_add_del_confirmation (const char *confirmation_id, int resync, GError **error);
 #endif
diff --git a/python/seafile/rpcclient.py b/python/seafile/rpcclient.py
index 34d34abc..ae5b5abb 100644
--- a/python/seafile/rpcclient.py
+++ b/python/seafile/rpcclient.py
@@ -211,3 +211,8 @@ class SeafileRpcClient(NamedPipeClient):
     def seafile_shutdown():
         pass
     shutdown = seafile_shutdown
+
+    @searpc_func("int", ["string", "int"])
+    def seafile_add_del_confirmation(key, value):
+        pass
+    add_del_confirmation = seafile_add_del_confirmation