diff --git a/paddle/framework/ddim.cc b/paddle/framework/ddim.cc
index d9d5e9f66e38aafb949bff789b242cc1a7d8a773..d2ef85afe55e640a17b8c957bac61d175e69ff3f 100644
--- a/paddle/framework/ddim.cc
+++ b/paddle/framework/ddim.cc
@@ -280,8 +280,6 @@ std::ostream& operator<<(std::ostream& os, const DDim& ddim) {
   return os;
 }
 
-ssize_t DDim::size() const { return arity(*this); }
-
 DDim::DDim(std::initializer_list<int> init_list) {
   *this = make_ddim(init_list);
 }
diff --git a/paddle/framework/ddim.h b/paddle/framework/ddim.h
index 0d10745a9e2f9cc6d8aa3e157b2723e8b9284d50..3976c6c0299c489764c7ccc209bef0a84736be12 100644
--- a/paddle/framework/ddim.h
+++ b/paddle/framework/ddim.h
@@ -52,8 +52,6 @@ struct DDim {
 
   DDimVar getVar() { return var; }
 
-  ssize_t size() const;
-
   bool operator==(DDim d) const;
 
   bool operator!=(DDim d) const;