The polarization-induced fading in fiber-optic sensor causes the decrease of interference efficiency,and the high cost in the use of polarization-maintaining fiber affects the practicability of fiber-optic sensor.Based on the Mach-Zehnder interferometer,an optic-fiber sensor configuration using partial polarization maintaining apparatus and feeding the interference signal back to the polarization controller to eliminate the polarization-induced fading is presented. And the system SNR is about 60 dB.