In the star light guidance of space vehicles, the optical lens design requirements for star tracker are critical to determine accurately the spatial location information and to improve the accuracy of navigation system. A new type of star tracker optical lens system is designed according to the requirements and the operation principle is presented. With the optical design and difference analysis, the optical system distortion is less than 0.2%, the axial spherical aberration is less than 0.1, which can meet the demand for high-precision astronomical navigation system.