Abstract: In order to study influence of multiple-beam interference on the transmittance of yttrium vanadate prisms, transmittance from 800nm to 2400nm was theoretically analyzed taking multiple-beam interference into consideration or not. Experiments were carried out with a UV-3101PC spectral photometer. It is found that transmittance of the prism increases and vibrates with wavelength. The result shows that multiple-beam interference makes a disturbance to the transmittance of the prism. It is a good reference to the application of yttrium vanadate prisms.