diff --git a/api/db/services/file_service.py b/api/db/services/file_service.py
index 367f39d82..60b51a0e4 100644
--- a/api/db/services/file_service.py
+++ b/api/db/services/file_service.py
@@ -432,7 +432,7 @@ class FileService(CommonService):
                 MAX_FILE_NUM_PER_USER = int(os.environ.get('MAX_FILE_NUM_PER_USER', 0))
                 if MAX_FILE_NUM_PER_USER > 0 and DocumentService.get_doc_count(kb.tenant_id) >= MAX_FILE_NUM_PER_USER:
                     raise RuntimeError("Exceed the maximum file number of a free user!")
-                if len(file.filename) >= 128:
+                if len(file.filename.encode("utf-8")) >= 128:
                     raise RuntimeError("Exceed the maximum length of file name!")
 
                 filename = duplicate_name(