Abstract: To improve dynamic tracking performance of the servo tracking system mounted with a small arm, a variable damping ratio control algorithm by fuzzy PID is proposed. Fuzzy PID control technique is employed to vary damping ratios of the system by adjusting feedback gains of velocity loop online, which consequently improve the systems dynamic performance. Simulation results indicated that variable damping ratio control algorithm by fuzzy PID is able to resolve overshoot and oscillation of the servo tracking system mounted with a small arm, and the system can work prospectively.