Taking a 30×continuous zoom lens as an example, the method of changing the pressure angle of the curve is researched. The pressure angle is taken as the objective function, and the cam curve rotation angle is constructed as a piecewise function to re-divide the angle, the position where the pressure angle is too large is distributed large rotation angle, and the rotation angle of position where the pressure angle is small is compressed, so as to reduce the overall pressure of the curve, and also to restrain the large inflection point effectively in the curve. The optimization results of various angular allocation values are compared with the simulation using Matlab and the optimal cam curve is obtained. The optimal result reduces the maximum pressure angle of the curve from the original 76.9° to 41.9°. The experimental results show that the zoom lens optimized by this method has good imaging quality, the line-of-sight liner is not more than 3 pixels, and the stability of the line-of-sight is not more than 1 pixel.