diff --git a/oneflow/core/memory/memory_case_util.cpp b/oneflow/core/memory/memory_case_util.cpp
index 9e75791c352b06e9e7f3ecd3bfcc28b24b6537e1..7977406648abf5f46a4f407589a84b27d95fd325 100644
--- a/oneflow/core/memory/memory_case_util.cpp
+++ b/oneflow/core/memory/memory_case_util.cpp
@@ -76,10 +76,6 @@ bool MemoryCaseUtil::IsHostUnPinnedMemoryCase(const MemoryCase& mem_case) {
          && !mem_case.host_mem().used_by_network();
 }
 
-int64_t MemoryCaseUtil::MergeThrdMemZoneId(int64_t thrd_id, const MemoryCase& mem_case) {
-  return (thrd_id << 21) | (MemoryCaseUtil::GenMemZoneId(mem_case));
-}
-
 std::shared_ptr<MemoryCase> MemoryCaseUtil::MakeMemCase(const DeviceType device_type,
                                                         const int64_t device_id) {
   const auto& mem_case = std::make_shared<MemoryCase>();
diff --git a/oneflow/core/memory/memory_case_util.h b/oneflow/core/memory/memory_case_util.h
index 235a0f1aa47ea3f2e3cc02d7775ec098fe2ce900..bfed8412ea972efa9e4b0822f5172136fa3ed44f 100644
--- a/oneflow/core/memory/memory_case_util.h
+++ b/oneflow/core/memory/memory_case_util.h
@@ -48,8 +48,6 @@ struct MemoryCaseUtil {
 
   static int64_t GenMemZoneId(const MemoryCase& mem_case);
 
-  static int64_t MergeThrdMemZoneId(int64_t thrd_id, const MemoryCase& mem_case);
-
   static bool IsHostUnPinnedMemoryCase(const MemoryCase& mem_case);
 
   static std::shared_ptr<MemoryCase> MakeMemCase(const DeviceType device_type,