Abstract: Backscatter noise is one of the main noises in resonator fiber optic gyro(RFOG). Based on the principle for reducing the backscatter noise by carrier suppression method, the mathematical model was established for the influence of temperature and voltage on the gyro bias. It is theoretically proved that this method is largely affected by temperature and has higher circuit requirements. A new scheme of RFOG based on three-mode differential technology was put forward. In this scheme, the backscatter noise is decreased by operating three beams with large frequency intervals in the resonant cavity. A comparative experiment was conducted with traditional two-mode closed-loop gyro. The results show that the new scheme can effectively minimize the gyro noise, and both the maximum gyro bias and bias stability are improved by around 4 times.