Due to disturbance movement of helicopter, the on-board servo system needs isolating the movement, and eliminating error between optical axis and target LOS. In this paper, servo motor was used as actuator and rate gyro and potentiometer were chosen as sensors. In view of mission requirement of tracking system, controllers of disturbance isolation loop and precise aiming loop were designed and a compensator for friction was also designed for servo system friction. Simulation result indicates that the aiming-tracking system has fast response and good stability, and gain excellent disturbance isolation ability and small aiming error, satisfying common performance requirement of fire control system.