Fiber optic current transducer (FOCT) overcomes the weakness of electromagnetic current transducer in transient current response and meets the demands of accurate current measurement of modern power system in real-time. Experimental research on FOCT’s dynamic character is done to ensure the system dynamic characteristics meet the practical requirements. A dynamic model is established based on the working principle of FOCT, and its transfer function is also deduced, so that the dynamic characteristics of FOCT can be evaluated. Furthermore, the relationship between several important parameters in the dynamic model and the closed-loop bandwidth is analyzed; the experiment result shows that system bandwidth is inversely proportional to the length of delay fiber optic cable and proportional to the gain of forward channel. And the bandwidth is proportional to important parameters of the gain of forward channel, such as gain adjustment coefficient, interference intensity, and sampling numbers. In order to guarantee the dynamic performance in the FOCT’s designing and using, theoretical basis and reference are provided in the choice of length of delay fiber optic cable and the parameters of the gain in forward channel.