Considering azimuth angle and elevation angle of star sensor, a new method about images simulation of star sensor was presented. Firstly, exact speed and position of star sensor platform and target were computed by NORAD TLE data and the SGP4/SDP4 model. Secondly, the relations of sensor coordinate system, spacecraft body coordinate system and J2000 geocentric inertial coordinate system were considered. Then the precise position and gray value of stars and targets in CCD images were computed, and sequence images were generated by accumulating stars image and target image. Finally, according to simulation result, movement characteristics of stars and targets in images were analyzed. The method is more reliable than traditional methods. The movement characteristic analysis is effective for dim target and helpful to detect target in star sensor images.