For the output ripple phenomenon caused by sampling frequency jitter of digital closed-loop fiber optic gyroscope control system, based on the discrete control system theory, the theoretical model of digital closed-loop fiber optic gyroscope under four-state square wave modulation was established. The stability conditions, steady-state errors and frequency response characteristics of the control system were studied, and the ripple free minimum beat control scheme of digital closed-loop fiber optic gyroscope was proposed. Through comparison with the original control system by experiments, the results show that the ripple free minimum beat control effectively eliminates the output ripple caused by sampling frequency jitter in the digital closed-loop fiber optic gyroscope control system, effectively improves the accuracy of the digital closed-loop fiber optic gyroscope, and the bias stability is improved by about 30%.