Interferometric fiber-optic gyroscope (IFOG) is a kind of fiber-optic sensor which measures the rotational angular rate relative to the inertial frame based on Sagnac effect. A demodulation method based on digital phase tracking (DPT) is proposed for IFOG. The rotation-induced Sagnac phase shift is tracked by a generated phase to demodulate the rotational angular rate. The digital phase tracking is accomplished by coordinate rotation digital computer (CORDIC) algorithm that has less logical resource consumption and faster computing speed. After evaluation in the digital signal processing system of a fiber-optic gyroscope,this scheme is able to demodulate rotational angular rate less than 200 °/s and demonstrates a scale factor nonlinearity of 1200 ppm with bias stability of 0.027 °/h.