The remotely-operated weapon station (ROWS) is a non-linear system with strong backlash, time-varying friction and time-varying moment of inertia. The active disturbance rejection controller (ADRC) was designed to improve the system's performance. Based on ADRC extended state observer to estimate the model uncertainty and external interference of the system, the system's ability of disturbance rejection was greatly improved. Experiment result shows that the system used ADRC technique has good dynamic performance. It takes only 2.62s for a 180° maneuver with no overshoot and no chattering.