A closed-circuit television (CCTV) monitor optical system is designed by using Zemax. The effective focal length of the system is 5 mm, the F-number and the full field of view angle are 2.8 and 70°, respectively. The image sensor of the lens is 1/2 inch CCD , whose pixel size is 6.5 μm×6.5 μm. To achieve the lens with compact feature in structure and wide field of view, an inversed telephoto system is used. According to the character of CCTV lens, some field currature remains, which can ensure the system has a high resolution. The result shows that 5 spheric lens can meet the requirement. The value of modulation transfer function (MTF) is more than 0.3 within 0.7 field of view (FOV) at the Nyquist frequency, the MTF value of FOV is more than 0.5 at the 1/2 Nyquist frequency. Various components are the spherical mirror, the form are simple, and the structure is compact.