diff --git a/ge/graph/manager/graph_manager.cc b/ge/graph/manager/graph_manager.cc
index 01b527c4..0f63f8dd 100755
--- a/ge/graph/manager/graph_manager.cc
+++ b/ge/graph/manager/graph_manager.cc
@@ -539,7 +539,7 @@ Status GraphManager::OptimizeSubGraphWithMultiThreads(ComputeGraphPtr compute_gr
   // use default 16 multi thread
   uint32_t thread_num = 16;
 
-  const char *env = std::getenv("THREAD_MULTI_NUM");
+  char *env = std::getenv("THREAD_MULTI_NUM");
   if (env != nullptr) {
     thread_num = atoi(env);
     GEEVENT("OptimizeSubGraphWithMultiThreads thread num: %u", thread_num);