By rudiment introductions of PID regulator, it is indicated that setting parameters of PID regulator reasonably is key to eliminate any stirs and to realize quick, accurate and stable movement of mirrors. Through applications of PID regulator and actuator, it is improved the alignment of the reflecting mirrors in the resonator in the static state and mirrors may be real time aligned in the dynamic state to a certain degree. It is possible that the drift and deformation for COIL output beam spot is reduced.