Abstract: Based on conventional optical current sensor, a new measuring technology of optical current sensor with four paths was put forward. As its four output signals were accurately able to obtain the azimuth of polarization, the measuring scope of current was out control of the monotone zone of sine function and was enlarged. In order to assist optical current sensor with four paths, a new experimental data processing method with arc-tangential function was introduced. As it didn't exist insensitive zone and was able to correct the drawback of original data, it could enhance measuring precision. The whole current which was shutter's short circuit through the magneto-optical sensing element with 14 times was measured at 4.5 kV voltage and 50 μF capacity. In agree with theoretical calculation val