Optimization design of partially compensating lens is one of the key problems for aspheric surface testing using partially compensating lens. A design method for the partially compensating lens based on Zemax, which takes the slope of wave-front as the optimization objective, is proposed. First the relation among residual wave-front slope, and interference fringe density and dispersive spot are analyzed, leading to the conclusion that the dispersive spot can quantitatively characterize the residual wave-front slope and its radius is taken as the optimization target. Then the method is applied to the optimization design of partially compensating lenses corresponding to three kinds of aspheric surfaces. The results indicate that, on the precondition that the interference fringes are detectable, the method can help complete the optimization design of partially compensating lens more simply, faster and more visually, resulting in decrease of the residual wave-front slope and reduction in the interference fringes density. Therefore, the measurement range of the interferometer for testing aspheric surface is expanded, and aspheric surfaces with higher spatial frequency can still be measured without increasing the resolution of interferogram detector.