In order to improve transmittance and reduce the distance between two emergent waves, we design a new high extinction ratio prism. We analyse three aspects of the prism, including the polarized state of emergent lights, beam path and transmittance in theory,and measure the performance of the coated sample. Form the theoretical analysis and the experimental results we can generalize that this proposed prism not only attains transmittance and reduces the distance between two emergent waves. This prism satifies our requirement.