Abstract: A novel resonant-interferometric fiber optical gyroscope is proposed in the paper, the formula of optical intensity transmittance of the RIFOG's is deduced,the sensitivity of the rotation of the REFOG, RFOG and the RIFOG is compared.The system scheme of the RIFOG is designed, and as shown by the theoretical analysis, the system with 3-meter-length of polarization maintaining fiber ring-resonator and optical amplifier in it can get theoretical resolution better than 22o/h.