Abstract: In order to study the birefringence effect of liquid crystal in communication,the transmission of liquid crystal electric-dependent was analyzed by means of the polarized light interference method and tested with a UV-3101PC spectral photometer at room temperature 20℃.The electro-optic effect of liquid crystal was studied by altering voltages at wavelengths of 1300nm and 1550nm.The result showed that there was a high transmission bandwidth nearby 1550nm when the voltage was 2V of the liquid crystal,and there was a high transmission bandwidth nearby 1300nm when the voltage was 2.3V of the liquid crystal. The conclusion is helpful for designing of liquid crystal device in communication.