diff --git a/mindspore/ccsrc/optimizer/opt.cc b/mindspore/ccsrc/optimizer/opt.cc
index c9f58039029e582200e3bbebb08cde7230e1f8c7..7ed6a93934cdf6c2c1bab2a7c16f66382c7d6eab 100644
--- a/mindspore/ccsrc/optimizer/opt.cc
+++ b/mindspore/ccsrc/optimizer/opt.cc
@@ -110,6 +110,7 @@ bool SubstitutionList::ApplyTransform(const OptimizerPtr &optimizer, const AnfNo
   auto seen = NewSeenGeneration();
   // 1024 is for the initial capacity of deque
   std::deque<AnfNodePtr> todo(1024);
+  todo.clear();
   todo.push_back(root_node);
   bool changes = false;