Phenomena of self-coherence and mutual-coherence of the distributed fiber optic sensor based on the principle of polarized-mode coupling are analyzed. The inter ference characteristics measured by experiment validate the theoretical analysis . The spatial resolution of the distributed fiber optic sensor is determined by the polarized dispersion coefficients of polarization-maintaining fiber and the spectral width of the light source. The spatial resolution of the polarized-mode s coupling distributed fiber optic sensor measured by experiment is 6cm.