The polarization lidar returns exist a depolarization signal in liquid water clouds due to the occurrence of multiple scattering when the optical and microphysical characteristics of liquid water clouds are detected by lidar. The detailed process of semi- analytic Monte Carlo simulation is given to study the backscattering depolarization of polarization lidar. The backscattering Muller matrix 2D images are given for the liquid water clouds with the laser at 0.532 μm as the light source. The 2D images of backscattering Stokes parameters are given for the horizontal linear polarization, vertical linear polarization, +45° linear polarization and right circular polarization states of light incidence. The depolarization and the polarization ratios are given for different lidar receiver field of view angles and depth from the cloud base. From the results, it can be seen that the impact of multiple scattering increases with the increase of receiver field of view angle. The proposed Monte Carlo simulation method has great value for remote sensing of water clouds and spherical aerosol characteristics.