Abstract: In order to measure the liquid crystal birefringence,a simple and accurate method called polarization interferometry was used from the theoretical formula of polarized light interference and by making a certain approximation. More satisfactory data were achieved by theoretically analysis and experimental verification. The results show the use of polarized light interferometry to measure the liquid crystal material avoids the measurement of the absolute intensity of transmission spectrum, and has high accuracy. It is helpful for the design, manufacture and application of liquid crystal device.