The influence of atmospheric transmission and object reflection on polarization properties of circularly polarized laser beam was studied.Based on the Monte Carlo method and with Stokes-Mueller matrix form,we used Mie scattering theory and polarized bidirectional reflection function model to trace the polarization state of each photon,made statistics and analysis to Stokes vector and polarization information of the final polarized light.The result of simulation shows that:With visibility of 23 km,distance of 100 km,target refractive index of 1.44+5.23i and surface roughness of 0.1 mm,the atmosphere has less influence on the polarization properties,while the target reflection has greater influence on the polarization properties;and the circular polarized light turns into elliptical polarized light at the receiving end.