Hi SUIYAN, it is likely that there is some problem with the projection step, probably the projected curve is not well formed.

Did you use the "Closest point" option in the project command? That particular option can make a sort of wiggly curve result if the curve is not within a small distance of the surface.

You will probably need to use a different method than current way you have done the projection.

It would be easier to help you if you can please post a .3dm model file with the actual objects you show with your question instead of only screenshots.

- Michael