Abstract: In the final course of zoom lens design, the cam curves have to be designed. In addition, in order to balance the uniformity between imaging magnification change and cam corner, the appropriate cam curve should be chosen. So it is important to establish the relationships between imaging magnification M and cam corner . Based on the boundary conditions and the continuity of the function whcih cam curves have to meet, some functions are established and discussed. Some design examples were simulated with Matlab, which indicates that the exponential function fits well with M and . Besides, the pressure angle is less than the permitted value and the uniformity of cam curves is better and smooth without cam inflexions. Compared with other solutions used before, this method helps the designer to modify the cam curves effectively and find the best cam curves of the zoom lens.