Abstract: The main polarization mode and coupling mode in polarization-maintaining fiber (PMF) have some optical path difference because of the internal birefringence. White-light interferometry for testing continuum polarized coupling distributing and discreting polarized coupling distributing in high birefringent waveguide was investigated. The polarization-maintaining parameter was obtained and a concise formula was derived. It can be used to measure the intensity and position of the coupling point accurately according to the relevant theory of modulation and demodulation. PMF and the optical fiber polarizer were measured as examples. The new approach can be utilized to test integrated waveguide elements, PMF, the axis alignment between birefringent waveguide, distributed optical fiber sensors, etc, The most prominent advantage of this method is to measure the polarization-maintaining parameter without any destruction to PMF. It can be used as an effective testing tool in PMF manufacture and application. With the help of this detection method, the performance of optical fiber polarization devices and optical fiber sensors is improved significantly.