The visibility of output stripes from a fiber interferometer is affected by the polarization fading caused by the birefringence effect of a single-mode fiber. To solve this problem, we propose a simple depolarization fading method. This method can also realize the space point detection of an optical fiber interferometer sensor. A sensor probe with a built-in Faraday rotator which is with a rotation angle of 45° is designed, and a Faraday rotating mirror with a rotation angle of 45° is used. They are added in the two ends of a Michelson fiber interferometer. In this paper, the interferometer system is theoretically calculated and analyzed, and the visibility measurement experiment of the interferometer is carried out when the external environment and the polarization controller are changed. The results show that this method can effectively overcome the polarization fading of the fiber interferometer when we conduct the point detection in the outside world, and it can obtain the interference stability with variation less than 0.9%.