diff --git a/api/core/workflow/graph_engine/graph_engine.py b/api/core/workflow/graph_engine/graph_engine.py
index 57e4f716fd..8342dbd13d 100644
--- a/api/core/workflow/graph_engine/graph_engine.py
+++ b/api/core/workflow/graph_engine/graph_engine.py
@@ -180,16 +180,20 @@ class GraphEngine:
 
             # trigger graph run success event
             yield GraphRunSucceededEvent(outputs=self.graph_runtime_state.outputs)
+            self._release_thread()
         except GraphRunFailedError as e:
             yield GraphRunFailedEvent(error=e.error)
+            self._release_thread()
             return
         except Exception as e:
             logger.exception("Unknown Error when graph running")
             yield GraphRunFailedEvent(error=str(e))
+            self._release_thread()
             raise e
-        finally:
-            if self.is_main_thread_pool and self.thread_pool_id in GraphEngine.workflow_thread_pool_mapping:
-                del GraphEngine.workflow_thread_pool_mapping[self.thread_pool_id]
+
+    def _release_thread(self):
+        if self.is_main_thread_pool and self.thread_pool_id in GraphEngine.workflow_thread_pool_mapping:
+            del GraphEngine.workflow_thread_pool_mapping[self.thread_pool_id]
 
     def _run(
         self,
diff --git a/api/core/workflow/nodes/iteration/iteration_node.py b/api/core/workflow/nodes/iteration/iteration_node.py
index 6f20745daf..01bb4e9076 100644
--- a/api/core/workflow/nodes/iteration/iteration_node.py
+++ b/api/core/workflow/nodes/iteration/iteration_node.py
@@ -89,6 +89,7 @@ class IterationNode(BaseNode):
             variable_pool=variable_pool,
             max_execution_steps=dify_config.WORKFLOW_MAX_EXECUTION_STEPS,
             max_execution_time=dify_config.WORKFLOW_MAX_EXECUTION_TIME,
+            thread_pool_id=self.thread_pool_id,
         )
 
         start_at = datetime.now(timezone.utc).replace(tzinfo=None)