Star tracker is a high accurate attitude measuring instrument used in various spacecrafts. The operation process of the star tracker consists of stars imaging on focal plane through optical lens

star light-to-charge conversion with a CCD sensor

preprocessing of star signal for eliminating noise

centroid calculation with sub-pixel algorithms

and at last the attitude computing and coordination conversion. In this paper

the operation process simulation is implemented except the attitude computing. Some simulation results are given in the paper. The method used in the paper is useful for evaluation of star tracker performance. This software can be used in both various space sensors development and astronomical research. But

if it is used in astronomical research

atmospheric effect must be taken into account.