attachment file have two curves,infact they have two intersect points,but I just can get one point use Intersect command or use c++ sdk function.cs.rar (75.8 KB)

In fact, no, the two curves miss each other by .002 at the upper point, and your file tolerance is .001, so they technically do not intersect at that point.

HTH, --Mitch

but I use c++sdk function and set the tol equl to 0.1,still just can get one point

Using this sample on your model with an intersection tolerance of 0.1 returns 2 intersection events (and thus two points).