In this essay, we developed an environmental immunity of multiplexed In-line sagnac interferometric fiber-optic current sensing system. The multiplexedwas used the time-division technique, were proposed to meet this research objective. The theoretical inference and experimental results were presented. The experimental results the system have sensitivity 56£gV/A¡Eturns, and the signal to noise ratio is 70dB. Besides, the multiplexed sensed two current in the same time, those two responses are still linearity. The uniform of these multiplex sensed are less than 2%. The system is hysteresis-free operator, no saturation limit. These features are suit for fiber-optic current sensor in measuring large range variable current. The current waveform can be read directly. In this research, the result let the fiber-optic current sensor approach to application on industrial power delivery line and monitor more current by this system.