How to merge "curved surface"


i wanna merge curved surface such as that image

It seems that ordinary surface merge does not correspond to curved surfaces, what should I do?

mergeallfaces only works for planar surfaces.
In this case, you’d need to overbuild a larger surface then trim it back to your desired shape-

Try the _MergeSrf command which works for curved surfaces. Set the Smooth option to “No” to keep any hard edges. The surface on he right is now one surface.

i guess you are trying to make a boolean union, merging is a different process and would not be applicable in this situation. maybe post a file if you have any problems with it. from this picture its not understandable what the issue is.