In this paper, we proposed a useful 3D mesh extrusion method for intuitive, efficient geometric modeling of free-form polygonal models. With our method, the user can sketch two strokes to extrude a polygonal mesh surface. Two remeshing techniques: partial mesh re-triangulation and mesh optimization are described in this paper first. After that, the extrusion algorithm with the remeshing techniques is introduced in detail. The method can be widely used in the modeling of free-form polygonal objects. And at the end of this paper, several examples are given.