Abstract- When traveling through an optically thick medium, such as a cloud, multiple scattering from cloud particulates results in reduction of the degree of  polarization of  the incident Lidar signal. The returned signal to the Lidar receiver system will be partially-polarized(with a degree of polarization less than one). The amount of depolarization  depends on the characteristics of the scattering medium. In this paper, we have made use of Monte-Carlo simulations to study the depolarization of an incident polarized Lidar beam traveling through a layer of water droplets cloud. For this purpose, we have considered two cases of linearly polarized and circularly polarized incident light beams and compared the simulation results of this two states for different values of water droplets diameter and detector field of view(FoV).