Resonator micro optic gyroscope (RMOG) is a novel optical rotation sensor whose resonant frequency is changed due to the Sagnac effect. Optical ring resonator is the key sensing element in RMOG. Using one-point reflection to simplify the distributed backscattering phenomenon in the resonator,combining the overlapping method of multiple beams,backscattering spectrum is theoretically formulated. On this basis,when the laser frequency is swept linearly to time,the resonance curve and the backscattering curve are measured on the polarization maintaining silica optical ring resonator. The backscattering coefficient is successfully obtained. Simulation shows that the experiments fit well with those obtained theoretically. It will supply the theoretical support to make research on the backscattering induced noise in RMOG.