A depolarizer is usually used to reduce the polarization response of the spectrometer. On the basis of LYOT depolarizer, a depolarizer composed of two quartz crystals with the same wedge angle is designed and developed. Based on the matrix optics theory, this paper studies the relationship between the residual polarization degree of a LYOT depolarizer and the polarization angle of incident light, wavelength, spectral bandwidth, crystal central thickness. The residual polarization degree of a LYOT depolarizer is tested on the polarization sensitivity tester, and the test results are in good agreement with the theoretical analysis results. The LYOT quartz depolarizer can meet the requirements of spectral radiation measurement, and is of strong engineering practice.