Abstract: To achieve good performance with short length, an ultra-thin cell phone lens was designed with optical plastic as lens material by optimizing the initial structure. The lens included four pieces with even aspheric, and the aperture was placed in front. The length of the lens was 4.49mm, the F number was 2.4, the viewing angle was 65.5, and the focal length was 3.71 mm. The MTF at the Nyquist frequency and half-Nyquist frequency of the detector was respectively greater than 0.14 and 0.46 and distortion of the lens was less than 1.5%. The RMS radius of different fields was less than 3.5 m. The CMOS sensor IMX111 from SONY was adopted, and the maximum resolution was 3 2642 488. By simulation, the defocusing amount of the cell phone was 144 m. By focusing, high quality images can be obtained when the object distance was greater than 10 cm. Through the sensitivity analysis, the tolerance of the lens met the processing requirements. With short length and aspherical plastic lens, the production cost is low, the imaging performance is good, which meet the practical requirements of cell phone lens.