diff --git a/x2paddle/op_mapper/paddle2onnx/opset11/paddle_custom_layer/multiclass_nms.py b/x2paddle/op_mapper/paddle2onnx/opset11/paddle_custom_layer/multiclass_nms.py
index 7060cfbeebcaf69bbb9543774661e8b914aae287..f953ad99d38958f1f8e6fc9927086401a4f28014 100644
--- a/x2paddle/op_mapper/paddle2onnx/opset11/paddle_custom_layer/multiclass_nms.py
+++ b/x2paddle/op_mapper/paddle2onnx/opset11/paddle_custom_layer/multiclass_nms.py
@@ -72,7 +72,7 @@ def multiclass_nms(op, block):
             dims=(),
             vals=[float(attrs['nms_threshold'])]))
 
-    boxes_num = block.var( outputs['Out'][0]).shape[0]
+    boxes_num = block.var(outputs['Out'][0]).shape[0]
     top_k_value = np.int64(boxes_num if attrs['keep_top_k'] == -1 else attrs['keep_top_k'])
     node_keep_top_k = onnx.helper.make_node(
         'Constant',
diff --git a/x2paddle/op_mapper/paddle2onnx/opset9/paddle_custom_layer/multiclass_nms.py b/x2paddle/op_mapper/paddle2onnx/opset9/paddle_custom_layer/multiclass_nms.py
index 57d8a7467789e3bead12c2d3ffaf86a95c397cf8..6d8172fc63c7441ff96b49da44ea700d5700289e 100644
--- a/x2paddle/op_mapper/paddle2onnx/opset9/paddle_custom_layer/multiclass_nms.py
+++ b/x2paddle/op_mapper/paddle2onnx/opset9/paddle_custom_layer/multiclass_nms.py
@@ -72,7 +72,7 @@ def multiclass_nms(op, block):
             dims=(),
             vals=[float(attrs['nms_threshold'])]))
 
-    boxes_num = block.var( outputs['Out'][0]).shape[0]
+    boxes_num = block.var(outputs['Out'][0]).shape[0]
     top_k_value = np.int64(boxes_num if attrs['keep_top_k'] == -1 else attrs['keep_top_k'])
     node_keep_top_k = onnx.helper.make_node(
         'Constant',