In order to improve the relative aperture of the star sensor and broaden the spectral range of the detection, the detector sensitivity calculation model was applied to determine the parameters of the optical lens in a star sensor, then an optical lens based on satellite platform was designed. The lens was composed of 7 spherical lenses, with the spectral region of 500-800 nm, the focal length of 50 mm, the relative aperture of 1/1.25, the field of view(FOV) of 8.45°×8.45°, and the total length was 83.33 mm. This lens used the telecentric structure in the image to reduce measurement errors caused by image defocus and other factors. After the optimization, the lens distortion was less than 0.5%, the center of mass color deviation was controlled within ±2 ?滋m, and the diffraction encircled energy (within 3×3 pixel) was greater than 80%, the maximum magnification chromatic aberration was -0.073 ?滋m, the dispersion spot energy concentration of all the fields of view was almost the same. In different temperature environments, the small change in focal length of the system verified the athermalization. The optical lens had good image quality.