At low speed or zero crossings, the existed nonlinear effects such as friction, the fluctuation of the motor moment will make the system jitter heavily. Our researches focus on the analysis and compensation of the motor moment fluctuation when the optoelectronic tracking system works at low speed. Actually, other nonlinear factors at low speed are also checked. As the fluctuation is always presented in sine orderliness, a repeat controller that bases on the study law is applied to the tracking system. Both simulations and experiments show that with the repeat controller, the tracking precision increase about 3 times comparing to the PID one.