Because of the significant nonlinearity of fast steering mirror (FSM), which is actuated by lead zirconate titanate (PZT) stacks, designing a high-performance laser beam pointing stabilization system is always a difficult work. This paper reports an active disturbance rejection control (ADRC) based feedback control system for laser beam pointing stabilization of a high-power quasi-continuous-wave (QCW) Nd:YAG slab laser with a repetition frequency of 160 Hz and an average output power of 1.5 kW. The simulation and experiment show that the ADRC is faster and smoother than traditional proportional-integral-differential (PID) control, and the ADRC can effectively reduce overshoot in the laser beam pointing stabilization process.