For machining auto-mobile cam, the developed biarcs-fitting method eliminates the ridge problems in conventional straight-line fitting approximation or single-arc fitting of curve tool path where it leaves ridges of tool marks on the machined surface of the workpiece. The powerful advantage of this biarc method is demonstrated by applying it to the numerically controlled machining of a curved cam profile, also verified by using a CNC simulating program for auto-mobile cam profile. As a result, this algorithm may be used in CNC milling and turning for cam profile machining with short block line.