A new structure of optical current sensor is designed in this paper. The COMSOL software is used to simulate the transmission field of optical sensing system. The responsiveness of symmetry optical path reflection type optical current sensor to Faraday effect can be obtained by the simulation study. The results show that the sensitivity of current sensor of symmetry optical path reflection type optical is 580 times higher than the sensitivity of traditional linear type optical current sensor. Finally the influence rule of measuring result error caused by sensing area positional deviation is analyzed. Further study about potential application of optical current sensor will proceed based on the optical current sensing system of symmetry optical path reflection type.