The distributed polarization mode coupling caused by stress field in high-birefringence polarization-maintaining optical fiber(PMF) was measured and analyzed using a scanning Michelson white light interferometer.The magnitude of the stress was calculated according to the intensity of the polarization mode coupling.The location of the stress was determined by calculating the optical path difference of the two orthogonal polarization modes.The structure of this distributed optical fiber sensor was proposed based on the theoretical analysis and numerical simulation.The measurement range is 1 km.The spatial resolution of the stress is on the order of millimeters.And the sensitivity of polarization mode coupling is approximately -80 dB.