It is difficult to verify the dynamic model of the digital closed-loop fiber optic gyroscope (FOG) due to the limitation of the turntable′s output frequency. To solve this problem, a novel evaluation method based on the magneto-optic Faraday effect is developed. The Sagnac phase difference is substituted by the Faraday phase difference induced by alternating current (AC) to eliminate the limitation of stimuli. Based on the dynamic system model of the FOG, the relationship between bandwidth and the parameters is analyzed and the system transfer function is obtained. The frequency response characteristic of the gyro is simulated via the obtained transfer function. Finally, some experiments are conducted to investigate the dynamic performance of the gyro. The experimental data are in agreement with the theoretical findings, which demonstrates the correctness of the dynamic model and provides the groundwork for optimizing dynamic characteristics.