The influence of polarization fluctuation noise and backscattering noise on the fineness of the resonant fiber optic gyro was analyzed. And an optical fiber ring resonance ring test system was set up. The experimental results show that, by using a polarization controller and a polarization maintaining light source to suppress polarization fluctuation noise, the fineness and the resonance depth of the characteristic parameters of the fiber resonance ring can be increased from 64.67 to 101, and from 0.5033 to 0.712, respectively. And the ratio of the backscattered light to the main signal intensity in the fiber resonator was measured to be 0.0267%. The research results can provide a theoretical reference for the miniaturization and high sensitivity of the resonant fiber optic gyroscope in the future.