On the basis of applying three dimensional discrete formative technology to describing last surface, working principle of numerical controlled last carving machine is briefly introduced. Then the algorithm of ascertaining milling cutter machining position during the machining process is analyzed in detail. We establish a three dimensional reference frame with spatial analytic geometry and obtain the spatial equation of milling cutter rotary surface. According to last machining character, we put forward a machining algorithm named Minimal Distance Method and is used to calculate the milling cutter machining position. Finally, the glabrous degree of last made by us has reached the conventional demand.