Abstract: Digital-micromirror device has became the most popular device to create infrared image, because of its characteristics as high frame frequency, high spatial and temperature resolution and wide dynamic range. In order to avoid the occlusion and collision between the illumination system and the projection system in the infrared target simulator, a beam splitter prism need to be added, while the ordinary beam splitter prisms have the disadvantage of low light utilization. To solve this problem and improve the light energy efficiency of infrared target simulator, a new splitting method was given based on polarizing principle from physical optics basic theories, and a polarizing prism was designed. Light energy utilization was improved greatly, and satisfactory results were obtained.