after that got error , what is the problem with this ? guys thanks
Post the file if possible. Looks like you selected the wrong object(s) as the trim object.
find the curve hehe
ExtractSrf the two surfaces to trim.
Explode and rejoin the curve per surface - two curves.
Note that one does not go to the edge of the surface, but by just about the file tolerance:
yes Thx Mr.Pasca , i got your point , may be I should catch the curve not full on surface,
any other probably be troubleshoting problem ? hehe