Fast-steering mirror (FSM) is a device used for controlling the direction of a light beam precisely. This article proposed a method to compensate the residual error of a coarse stabilized platform with FSM driven by PZT to improve line-of-sight stabilization accuracy greatly. The high precision line-of sight (LOS) stabilization system was simulated. The results of simulation showed that the stability error of coarse stabilized platform is 110rad, and the stability error after FSM compensation is less than 8 rad. This method can improve the stabilization accuracy at least one order of magnitude.