Star sensor is a kind of instruments which is used in measuring the spacecraft attitude with its highprecision. It mainly consists of three parts: an optical system, an image sensor circuit and the control of data processing circuit, of which the optical system is the core part of in imaging forming system. In this paper, the optical star sensor system of large relative aperture, lager view, broad spectrum is designed. Through the improvements of the basic structure symmetric double Gauss, a kind of optical structures of optimization process with perfect imaging quality is realized on the stage of Zemax software. The system has a compact structure with its properties: 60 mm in focal length, F number of 1.5, field of view of 20°, and the range of working wavelength is 0.48~0.68 μm, and the ratio of length and focal length is 1.81. The structure is compact and it achieves some special requirements aberration. The end result of this system is to provide reference data for star tracker optical system design.