The resonant type optical gyroscope needs to use the laser frequency locking technology to realize the frequency locking of one path and detect the resonant frequency of the other path light. After the laser frequency lock is achieved,the gyroscope system will be affected by environmental factors to generate ultra-low frequency drift in the frequency lock loop,and the gain generated by the traditional proportional integral servo controller cannot be restrained. In this paper,the traditional proportional integral controller is adopted along the way,and the low-pass filter and integral controller are used together to form a new servo controller for laser frequency locking. The system improves the low-frequency gain of the frequency lock loop,inhibits the frequency lock road of ultra-low frequency drift. Its feasibility is proved through simulation theory,and system is tested. Allan variance in the measured frequency lock loop is 0.005 °/s,and the frequency lock road basically has no drift.