diff --git a/api/core/app/apps/workflow/app_generator.py b/api/core/app/apps/workflow/app_generator.py
index 369fa0e48..a18139e64 100644
--- a/api/core/app/apps/workflow/app_generator.py
+++ b/api/core/app/apps/workflow/app_generator.py
@@ -219,6 +219,9 @@ class WorkflowAppGenerator(BaseAppGenerator):
         # new thread with request context and contextvars
         context = contextvars.copy_context()
 
+        # release database connection, because the following new thread operations may take a long time
+        db.session.close()
+
         worker_thread = threading.Thread(
             target=self._generate_worker,
             kwargs={