Abstract: As a key component of the polarization-maintaining fiber optic gyroscope, the fiber coil is sensitive to the temperature which mainly shows that producing thermally induced nonreciprocity phase shift. To overcome this problem, a novel thermally induced nonreciprocity phase shift measurement method based on strain distribution was proposed in this paper. The strain distribution data of fiber coil at different temperatures was analyzed, and the model of optical path centering was established. Modifying the pigtail of fiber coil with the model, and the optical symmetry properties can be adjusted consequently. In order to verify the effect of our work, the modified pigtail was equipped to the gyroscope to test its performance, and the result shows the accuracy of the gyroscope becomes much better than before. The method proposed in this paper is helpful to increase the yield rate of fiber coil, and it also has the advantage of easy to carry out.