diff --git a/be/src/runtime/tablets_channel.cpp b/be/src/runtime/tablets_channel.cpp
index adaced0b76ebfd..266d4d45f184ae 100644
--- a/be/src/runtime/tablets_channel.cpp
+++ b/be/src/runtime/tablets_channel.cpp
@@ -215,6 +215,7 @@ Status BaseTabletsChannel::incremental_open(const PTabletWriterOpenRequest& para
     ss << "LocalTabletsChannel txn_id: " << _txn_id << " load_id: " << print_id(params.id())
        << " incremental open delta writer: ";
 
+    // every change will hold _lock. this find in under _lock too. so no need _tablet_writers_lock again.
     for (const auto& tablet : params.tablets()) {
         if (_tablet_writers.find(tablet.tablet_id()) != _tablet_writers.end()) {
             continue;
@@ -238,6 +239,7 @@ Status BaseTabletsChannel::incremental_open(const PTabletWriterOpenRequest& para
                                                           _profile, _load_id);
         ss << "[" << tablet.tablet_id() << "]";
         {
+            // here we modify _tablet_writers. so need lock.
             std::lock_guard<SpinLock> l(_tablet_writers_lock);
             _tablet_writers.emplace(tablet.tablet_id(), std::move(delta_writer));
         }
@@ -479,6 +481,7 @@ Status BaseTabletsChannel::_open_all_writers(const PTabletWriterOpenRequest& req
 #endif
 
     int tablet_cnt = 0;
+    // under _lock. no need _tablet_writers_lock again.
     for (const auto& tablet : request.tablets()) {
         if (_tablet_writers.find(tablet.tablet_id()) != _tablet_writers.end()) {
             continue;
@@ -578,6 +581,11 @@ Status BaseTabletsChannel::add_batch(const PTabletWriterAddBlockRequest& request
                                  std::function<Status(BaseDeltaWriter * writer)> write_func) {
         google::protobuf::RepeatedPtrField<PTabletError>* tablet_errors =
                 response->mutable_tablet_errors();
+
+        // add_batch may concurrency with inc_open but not under _lock.
+        // so need to protect it with _tablet_writers_lock.
+        std::lock_guard<SpinLock> l(_tablet_writers_lock);
+
         auto tablet_writer_it = _tablet_writers.find(tablet_id);
         if (tablet_writer_it == _tablet_writers.end()) {
             return Status::InternalError("unknown tablet to append data, tablet={}", tablet_id);
diff --git a/be/src/runtime/tablets_channel.h b/be/src/runtime/tablets_channel.h
index 54438be7690db8..8ed4c7ab1aa3c8 100644
--- a/be/src/runtime/tablets_channel.h
+++ b/be/src/runtime/tablets_channel.h
@@ -136,11 +136,8 @@ class BaseTabletsChannel {
     // id of this load channel
     TabletsChannelKey _key;
 
-    // make execute sequence
+    // protect _state change. open and close. when add_batch finished, lock to change _next_seqs also
     std::mutex _lock;
-
-    SpinLock _tablet_writers_lock;
-
     enum State {
         kInitialized,
         kOpened,
@@ -166,8 +163,10 @@ class BaseTabletsChannel {
     // currently it's OK.
     Status _close_status;
 
-    // tablet_id -> TabletChannel
+    // tablet_id -> TabletChannel. it will only be changed in open() or inc_open()
     std::unordered_map<int64_t, std::unique_ptr<BaseDeltaWriter>> _tablet_writers;
+    // protect _tablet_writers
+    SpinLock _tablet_writers_lock;
     // broken tablet ids.
     // If a tablet write fails, it's id will be added to this set.
     // So that following batch will not handle this tablet anymore.