Abstract: A mobile phone lens assembly composed of 4 plastic aspheric lenses and an IR filter was designed by use of ZEMAX (optical engineering software). Considering the production and cost，the plastic lens E48R was chosen．The 1/3.2 in (7.94mm) 5 mega-pixel CMOS made by Aptina is taken as the image sensor of the lens assembly，whose pixel size is 1.75m and the limiting resolution is 285lp/mm. The F-number and FOV of the camera are 2.85 and 60 respectively. The results show that the lens has excellent imaging quality, the MTF value is more than 0.3 within 0.7 FOV at the Nyquist frequency, the MTF value of FOV are more than 0.5 at the 1/2 Nyquist frequency, wavefront mean square error is less than 0.1, and the distortion is less than 1％.