diff --git a/byte_micro_perf/core/perf_engine.py b/byte_micro_perf/core/perf_engine.py
index b20d0912..24af158e 100644
--- a/byte_micro_perf/core/perf_engine.py
+++ b/byte_micro_perf/core/perf_engine.py
@@ -249,6 +249,8 @@ def start_engine(self) -> None:
         output_dir.mkdir(parents=True, exist_ok=True)
 
 
+        op_name = self.workload["operator"]
+
         # get input shape info
         target_group_list = self.workload.get("group", [1])
         target_group_list.sort()
@@ -304,6 +306,8 @@ def signal_handler(signum, frame):
                 
             # get actual instance num
             instance_num = min(device_count, max(1, self.args.parallel)) if group == 1 else group
+            if group == 1 and op_name in ["host2device", "device2host"]:
+                instance_num = 1
 
             input_queues = mp.Queue()
             output_queues = mp.Queue(maxsize=1)