Abstract: In order to get the depolarization performance of a dualistic birefringent crystal,the performance of white light through it with different optical axis angles and thicknesses was dicussed.A the performance of the single crystal depolarizer and the Lyot depolarizer was proved through experiments.Some conclusions are drawn as follows:there are some indirect impacts on polarization with different optical axis angles;the thickness has a vital impact on polarization;the ratio of the thickness has a direct impact on polarization.These conclusions can give theoretic analysis and reference to the design and application of the depolarizers.