By theoretically analysing white-light interferometer and the testing principle of polarization coupling (PC) in polarization maintaining fiber (PMF) based on white-light interferometer,a fiber Michelson interferometer testing system of polarization coupling in polarization maintaining fiber based on white-light interferometer is designed. Testing experiments of polarization coupling in PMF are made and a good result of 70 dB detection sensitivity is obtained. The feasibility and veracity of polarization coupling testing based on white-light fiber Michelson interferometer are validated. Finally,a small PMF coupling coefficient is tested using different light sources including super luminescent diode (SLD),amplified spontaneous emission (ASE) and erbium-doped fiber amplifier (EDFA). Then we get the measurement error of 0.36%,1.8% and 2.5% respectively,which verify the accuracy of the testing system.