Aiming at completing functional tests on high precision star sensor of stars′ positional accuracy and star magnitude, an optical system of liquid crystal on silicon (LCOS)-based and high precision dynamic star simulator is designed. The general designing program is presented after the analysis of the collimating and the illuminating optical system. In order to improve the simulating precision, a optical splicing method of LCOS is put forward, designing process of a collimating optical system with large field of view, large relative aperture and long exit pupil is given in detail as well as the aberration diagrams. To satisfy the illuminating conditions ordered by LCOS and achieve simulation of -1 to 7 magnitude stars, an illuminating optical system is emulated. Experimental test indicates that the angular distance accuracy is less than 12″, and -1 magnitude to 7 magnitude stars can be simulated, which meets the calibration requirements of high precision star sensor.