diff --git a/paddle/fluid/framework/parallel_executor.cc b/paddle/fluid/framework/parallel_executor.cc
index 8630e51d0dfd195ea2a243e1f6a9a2195ac2920f..aa52cbb7bf21b5168e59c3d1a78def1e92adbee5 100644
--- a/paddle/fluid/framework/parallel_executor.cc
+++ b/paddle/fluid/framework/parallel_executor.cc
@@ -251,7 +251,7 @@ struct FetchOpHandle : public OpHandle {
 
 class ParallelExecutorPrivate {
  public:
-  explicit ParallelExecutorPrivate(size_t num_threads = 0)
+  explicit ParallelExecutorPrivate(size_t num_threads = 12)
       : pool_(num_threads == 0 ? nullptr : new ThreadPool(num_threads)) {}
 
   std::vector<platform::Place> places_;