Abstract: In order to improve the tracking accuracy of acquisition, tracking, and pointing (ATP) system of the laser communication, the method of discrete sliding mode control based on an exponential reaching law is presented in this paper. The tracking control model of the ATP system was established and the fine tracking system with sliding mode control was designed. Simulation of the dynamic lag tracking using designed system was conducted. The results show that, compared with conventional frequency domain method, the sliding mode control could increase control bandwidth and improve the stability and dynamic performance of the system. In addition, the coarse residual error of the system would be effectively suppressed in a wide range.