Liquid crystals with dielectric and optical anisotropy have the ability of optical phase efficient modulation. When the liquid crystal system is placed in external electric field, the director of liquid crystal system will be redistributed. In this paper, the optical modulated effect of electronically controlled liquid crystal light valve was studied experimentally and theoretically. The result shows that threshold voltage of light valve is about 4 volts. And when external voltage is higher than the threshold voltage, the transmitted intensity of liquid crystal light valve will present the aperiodic properties. According to the continuum elasticity theory model, the liquid crystal director distributions in the electric field were studied by numerical methods, and found that the aperiodic modulation of transmitted intensity is depending on the distribution of the liquid crystal directors critically. It is the theoretical and experimental basis for the study of polarization-modulation characteristics.