The laser with Porro prism resonator cavity has goog stability,and this structure has been widely used in military lasers.The polarization coupling property of Porro prism was theoretically analyzed.The relationship of different phase shift wave plate azimuth angles and polarization transmissivity was calculated by MATLAB software,and the change of polarization state was simulated in the process of optical coupling.Coupling properties of Porro prism with different materials were compared,and the results were verified through the experiments.This study has practical significance for the design of Porro prism resonator cavity and the selection of Porro prism materials.