Abstract: Based on triangular mesh model, A simple rapid method for swept volume of milling cutter moving in NC machining is presented. By utilizing the middle point line and 4-connected circle fill algorithm in the calculation of line-circle intersection, this method converts the multiplication/division operations into additions/subtractions. Additionally, an easily realized LOD (Level of Detail) scheme for reduction of triangles is also presented. By the scheme, the triangles in one pixel are combined into bigger ones according to the coefficient of graphics display scale and then the triangles that have equal normal in non-characteristic sections are also combined. Experiments show that the efficiency of graphics display is improved greatly.