In order to meet the market demand of optical zoom camera for mobile phone with low cost and high zoom ratio, the zoom system with three movement groups and the optical plastic-glass composite structure are used to design a camera lens for mobile phone with 4.6 times optical zoom, and 5 megapixels (5×106 pixel) resolution. The zoom system is optimized with computer-aided design software Zemax. In the whole field of view (FOV), the modulation transfer functions (MTFs) at 20 lp/mm are higher than 0.8, and the MTFs at half Nyquist frequency of CMOS in most part of the FOV are greater than 0.4 lp/mm at the wide-angle end (short focus) and the telephoto end (long focus). The relative distortion is less than 3.2%. The relative illumination at the wide-angle end is greater than 67%, and it is higher than 89% at the telephoto end. The moving curves change smoothly. The camera system has the advantages of high resolution, low manufacturing cost, and high zoom ratio.