In this paper, a novel method to measyre the distributed polarization mode coupling in poladzation-maintaining (PM) fibers is introduced. The measuement system is based on white light interference. A super luminescent diode is used as the broadband light source in the system, The whole test system is working on 130Ohm wavelength. There are two main palls of the measurement equipment: poladzation adjustment and a scanned Micbelson interferometer. In order to improve the accuracy, a piezoelectric transducer (PZT) is applied in the scanned Micbelson interferometer. The maximum length of tested polafizadon-maintnining fiber is one kilometer, and the spatial resolution of this method reacbed 60mm along the tested PM fiber, The degree of polarization mode coupling that could be detected is-75dB.