Hi JINYICOOL, or another possibility is to use Construct > Blend.

To do that, delete this bottom piece:


Restore this plane:


Then you can select these edges and do a Construct > Blend:


- Michael

Thanks, this gives me a new idea, and I think the mixed curvature result is smoother and more perfect.

Dear all,

The NSIDED command will solve this particular problem. It can be found on Construct.

By using a GIF image, I will demonstrate how to do it. It's very easy to do. I hope you are able to accomplish it.

Regards

Ray.