According to the design requirements of the birefringence of polarization-maintaining fiber in the non-line-of-sight azimuth transmission system, the influence of different types of polarization-maintaining fiber parameters on the birefringence is emphatically analyzed. Firstly, the stress-optical coupling relationship of polarization-maintaining fiber was deduced based on the stress-strain, variational principle and the stress-photoelastic effect. Then, the influence of different factors on the birefringence of polarization-maintaining fiber was investigated by means of finite element analysis software, and two kinds of polarization-maintaining fiber (Panda polarization-maintaining fiber and Bow-tie polarization-maintaining fiber) were compared and analyzed. The results show that the higher birefringence value near the center of the core can be obtained by a variety of methods, such as reducing the distance between the core and the stress zone, increasing cladding radius when fixing core size, or increasing the reference temperature of the polarization-maintaining fiber. Simultaneously, the birefringence of the bow-tie polarization-maintaining fiber is larger in the same conditions. The research results can provide some reference for the design and selection of polarization-maintaining fiber in the non-line-of-sight azimuth transmission system.