Abstract: Adopting the means of light vector superimposition, the polarization states of linearly polarized light transmitting through several wave-plates with arbitrary thickness were analyzed. Taking two wave plates whose optical axes are oriented at 45° as example, the polarization states and intensity of transmitted light were calculated. It is found that the polarization states are dependent on retardation of the back wave-plate, and the intensity is dependent on retardation of the front wave-plate and vibration azimuth angle of incident light. It also indicates that the characteristics are not the same when the two wave plates are used in forward and reverse directions. The theoretical results can be applied to the analysis of depolarizer, such as Lyot depolarizer.