Abstract: A new type of basic form of arc spline curve, namely symmetrical variable curvature circular arc (SVCCA) was developed to locally modify and optimize the profile of arc spline curve. Its calculation and practical application are described. By adopting SVCCA, both the maximum radius of curvature and the maximum difference of radii between adjacent arcs can meet the needs of computerized numerical control machining, especially computerized numerical follow-up control machining.