In order to realize the equidistance offset of the STL model, the vertex offset method for STL model offset based on the area weighted average was studied. The software system was implemented by using the VC++60, C++ and OpenGL, and the comparative analysis between the offset model generated by the proposed algorithms and the UG software was done by using the RapidForm XOV software. The case study shows that the standard deviations of the contour and cross profile between the two offset models are 1180 8 mm and 0022 8 mm respectively.