diff --git a/lite/kernels/x86/conv_compute.h b/lite/kernels/x86/conv_compute.h
index 063e66a1c19dc2250e1834a4d9dd2a22b0e5f6e4..e9f403059f90cf6635bc22db3e6890b86cbe85f6 100644
--- a/lite/kernels/x86/conv_compute.h
+++ b/lite/kernels/x86/conv_compute.h
@@ -65,7 +65,7 @@ class Conv2dCompute : public KernelLite<TARGET(kX86), PRECISION(kFloat)> {
       col_shape_vec[j + 1 + data_dim] = output_shape_vec[j + 2];
     }
     lite::DDim col_shape(col_shape_vec);
-    lite::DDim col_matrix_shape = col_shape.Flatten2D(data_dim);
+    lite::DDim col_matrix_shape = col_shape.Flatten2D(data_dim + 1);
     bool is_expand = IsExpand(
         filter_shape_vec, param.strides, *param.paddings, *param.dilations);
     lite::Tensor col;