Numerical control program is widely used in NC machining at present. A method of autoprogramming was proposed which was based on AutoCAD platform. VB was used as secondary development tool of the AutoCAD and a module was developed. The arcs and the aspheric curves were recognized in the part profile ,and the contour parameters of the complex curve were read by VB. The equalerror of the complex curve in NC programming was approximated by using VB, the NC machining program was generated automatically and the autoprogramming for complex curve milling machining was realized.