In this study, the components of fiber optic current sensor based on Faraday Effect such as polarizer, analyzer, laser, photodiode have been modeled and simulated by Matlab Simulink software, separately. Thus, the optimal performances of the components can be determined. The complete system sensor based Faraday's effect has been modeled by using of these sub-models and examined the effects of various dynamics. The obtained results have been analyzed and evaluated. Increasing number of turns of fiber wound for measuring of small currents has caused time lag of the system response. The output of system has not been affected by optical power of laser since it has been measured that the rotation angle of polarization of light.