Current NC machine tool was used to process aspherical curve,the machining accuracy is low due to the shortage of the interpolation principle.In view of the problem,a new speed interpolation principle was proposed.Through path curve decomposition and machine tool linkage control,high precision fitting between theory trajectory and actual trajectory of aspherical curve forming by CNC machine tool could be realized.The concrete implementation of the principle of speed interpolation process was discussed.By simulation and experiment analysis,the superiority of the proposed speed interpolation principle compared with traditional interpolation principle was demonstrated fully.