A novel method of reducing the threshold of the high precision digital closed-loop fiber optic gyroscope(DCFOG) is studied.The reason leading to the threshold increasing is proposed due to the gyroscope dead band which is mainly caused by the electronic cross-coupling interference in the modulation and demodulation circuit.The digital closed-loop transfer model for fiber-optic gyroscope is modified and the electronic cross-coupling interference from the feedback channel to the output signal of the detector in the forward channel is added.This model is also used to realize a real-time dynamic simulation for the dead band.The simulation results are basically consistent with experimental results.Unlike the random modulation method,this study inhibits the dead zone mainly by optimizing the electronic circuit and improving the circuit electromagnetic compatibility.We propose a new method to test the fiber optic gyro threshold.The results show that the gyroscope threshold is comparable to the noise level.