The invention discloses a Sagnac phase shift tracing method of an optical fiber gyroscope, belonging to the field of optical fiber sensors. The method comprises the following steps: 1) carrying out filter demodulation on the detected signal when K equals to zero to obtain first and second harmonic demodulation signals S1(0) and S2(0) when K equals to zero; 2) calculating the Sagnac phase shift (0) of the optical fiber gyroscope when k equals to zero based on the S1(0) and S2(0), and initializing the initial value of a phase offset parameter PB to zero; and 3) carrying out filter demodulation on the detected signals collected at a later K moment to obtain first and second harmonic demodulation signals S1(k) and S2(k) at the present moment; and based on S1(k), S2(k), a first harmonic demodulation signal S1(k-1) and a second harmonic demodulation signal S2(k-1) at the previous moment, determining a Sagnac phase shift (k) value at the present moment. The invention can greatly improve the dynamic range, precision and scale factor linearity of the high optical fiber gyroscope.