Abstract: To improve the symmetry of emergent beams of a polarization prism,based on the Wallaston prism,the emergent face is inclined with an appropriate angle,so that the symmetry which the beam-splitting angle relative to the incident light direction can be ensured in the case of a certain structure angle.Taking the 589.3nm sodium yellow light for example,the relation formula among the obliquity of the emergent face,the structure angle of the prism and the beam-splitting angle are deduced,and the change trend of the beam-splitting angle along with the emergent face is also analyzed.Two correlative designs are presented at the same time.The testing results indicate that the symmetry is excellent and the experiment value is almost identical with the theoretical value which shows this polarization prism is positively an ideal symmetric beam-splitting polarization device.