For the influence problem of the humidity on polarization transmission character under infrared wavebands, this paper applies Monte Carlo simulation for the common carbonaceous aerosol particles existing in nature. The influence of humidity on polarization transmission characteristics and polarization character difference under infrared wavelengths is researched. The results indicate that the Degree of Polarization (DOP), both linear and circular polarization, gradually rises with the increasing of humidity in the short wave bands; In the medium wave bands, the DOP of them descends with the increasing of the humidity; In long wave bands, the influence of relative humidity on DOP is minimal. To compare linear polarization with circular polarization, we demonstrate that the latter always performs better than the former in the short wave bands, whereas the former maintains its better polarization state. Therefore, in infrared polarization applications these conclusions introduce a method for the wavelength selection, humidity controlling and polarization state application.