Abstract: In order to design and use the splitting Lippich prism and the splitting Grand-Thompson prism,the splitting angle,separation angle and splitting ratio of light intensity were analyzed.The results show:the splitting angle and splitting ratio of light intensity of the splitting Lippich prism and the splitting Grand-Thompson prism are dependent on the structure angle and the vice structure angle;both the prisms have the same splitting angle and different light intensity splitting ratios if they have the same structure angle and vice structure angle.The separation angle about beam o and beame' is dependent on the vice structure angle: the design of splitting Lippich prism is better for the need of normal output of beam o;the design of splitting Grand-Thompson prism is better for the need of a big splitting angle.With optimum design symmetric beam splitting of light intensity can be achieved for both the prisms.The experiment data are in accordance with the theoretical results.