Basic research on five-axis NC machining of subdivision surface is presented. Research on Catmull-Clark subdivision surface, a method is presented by using computational geometry techniques to determine optimal tool position and orientation for 5-axis machining with torus end-mill: The normal vector of the subdivision surface vertex and the offset surface calculation are discussed firstly, then the rough machining model of subdivision surface is built and machined by using five-axis machining with the motion of the torus end-mill position and orientation according to the normal line of the surface. The tool position and orientation, cutting radius and tool path are calculated. Finally a computer simulation instantiation is given. This method improves the machining ability of subdivision surfaces.