利用解析法建立与回转体对应的曲面方程，进而推导出曲面间的交线（相贯线）曲线方程，并利用描点法作出两曲面立体的相贯线投影．用解析法取代作图法不仅使作图过程变为求点坐标的过程，而且可准确求出相贯线上极限位置点的坐标，使作出的相贯线投影更准确． The analytic method is used to establish the surface equation corresponding to the rotating body, and then the curve equation of intersection (intersection line) between the surfaces is deduced. And the projection of the intersecting line of the two surfaces is made by using the tracing point method. The method of analytic method instead of the drawing method not only changes the process of drawing into the process of finding coordinates, but also can obtain the coordinates of the limit position on the intersecting line accurately and make the projection of the intersecting line more accurate.