diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4e44d7976452e5269096e0817b63db5baa39f2c9..469203aaece477dc17619b4c93d5976e28e1e561 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,7 +18,8 @@ Please mark all change in change log and use the issue from GitHub
 -   \#2692 Milvus hangs during multi-thread concurrent search
 -   \#2739 Fix mishards start failed
 -   \#2752 Milvus formats vectors data to double-precision and return to http client
--   \#2767 fix a bug of getting wrong nprobe limitation in knowhere on GPU version
+-   \#2767 Fix a bug of getting wrong nprobe limitation in knowhere on GPU version
+-   \#2768 After building the index,the number of vectors increases
 -   \#2776 Fix too many data copies during creating IVF index
 
 ## Feature
diff --git a/core/src/db/DBImpl.cpp b/core/src/db/DBImpl.cpp
index de92f323bae1a6340a372eb6de68da49c90c5a75..752187675a4e16f58eb55553b9383af2190203dc 100644
--- a/core/src/db/DBImpl.cpp
+++ b/core/src/db/DBImpl.cpp
@@ -2390,7 +2390,7 @@ DBImpl::GetPartitionsByTags(const std::string& collection_id, const std::vector<
 Status
 DBImpl::UpdateCollectionIndexRecursively(const std::string& collection_id, const CollectionIndex& index) {
     DropIndex(collection_id);
-
+    WaitMergeFileFinish();  // DropIndex called StartMergeTask, need to wait merge thread finish
     auto status = meta_ptr_->UpdateCollectionIndex(collection_id, index);
     fiu_do_on("DBImpl.UpdateCollectionIndexRecursively.fail_update_collection_index",
               status = Status(DB_META_TRANSACTION_FAILED, ""));