Growing urban pollution leads to the rise of the carbonaceous particle content in the atmospheric environment. To further research the influence of the humidity on transmission characteristics of polarized light, radius, refractive index and the other parameters of aerosol particles at different humidities were studied, and through Monte Carlo method the transmission process of different incident light in carbonaceous medium was simulated, which could get the Stocks simulation pattern and polarization characteristics of the emergent light. The results show that the change of increase of the relative humidity can influence the polarization characteristic regularly. With the increase of the relative humidity, when the incident light is linear polarization, the polarization characteristics of emergent lights will have a increasing tendency, and can keep their polarization states; When the incident light is circular polarization, the degree of polarization(DOP) of the emergent light will have a maximum value at the humidity of 85%, and there will be no obvious regularity in the fluctuation of DOP and polarization angle. Therefore, when the incident light is linearly polarized light, the emergent light has a more advantageous in the polarization state keeping and polarization characteristic enhancement with the increase of the relative humidity.