利用蒙特卡罗方法模拟了多层离散随机介质对激光的偏振多次散射，结合激光雷达的特点，给出了半解析蒙特卡罗模拟方法的具体模拟步骤，考虑了光子在随机游走时，跨越分界层时引起的自由程调整，根据Mie 散射相函数对不同介质层进行了散射方向抽样，利用该方法计算了双层和三层水云的雷达多次散射去极化率随穿透深度的变化。从计算结果可以看出，随着穿透深度的增加，雷达去极化率增强，激光在从一种介质入射到另一种介质时，其去极化率增加的速度不同，分析了粒子有效半径、单次散射相函数以及消光系数对雷达去极化率的影响。该方法可以应用于偏振激光雷达对非各向同性云层或气溶胶微物理和光学特性的遥感反演。

The polarized multiple scattering of multi-layer discrete random media by laser is simulated by the Monte Carlo method. The simulation steps of a fast semi-analytic Monte Carlo method are given based on the properties of the polarization lidar. The free path adjustment is considered when the photon crosses the interface of different media. The scattering angles for different media layers are sampled based on the Mie theory. The relationship between lidar depolarization ratio and the penetration depth of two-layer and three-layer water clouds is studied. The results show that the depolarization ratio increases with the depth of penetration, and the increasing speed of depolarization ratio is also different when laser is incident from one medium to another medium. The influence of effective size, single scattering phase function, extinction on the lidar depolarization is analyzed. The method can be used to retrieve the microphysical and optical characteristics of inhomogeneous clouds or aerosols with the polarization lidar.