In a lot of application fields, it often needs to divide object outline into straight line and arc line. Because of many artificial objects (especially the machine processes spare parts) are combined with these two geometric lines. The purpose of this research is developing the system with figure conversion. That is to transfer the image acquisition of the leather component outlines into straight line and arc line. The first, find out the leather component outlines by using image processing technology, then determine the features of its outline by partial curvature maximum, and use the cosine angle of this outline to decide electable straight line, and then find out electable arc and the opposite approximate position by using arc combination. Finally, confirm minimal range error, electable line, starting point, terminal point, the center of a circle and radius etc.