Based on Mie scattering theory, the single scattering albedo and the phase-matrix function of dust aerosol particles during wavelength of 0.2~40 μm for solar radiation and earth-atmosphere long-wave radiation are calculated with the lognormal distribution function to describe the dust particles size distribution. The scattering intensity and polarization characteristics of light scattered by dust aerosol particles are studied at different relative humidity conditions. The results show that, the single scattering albedo has an evident change with the incident wavelength; the variation trend is identical at different relative humidity conditions; within the visible and near-infrared band, the single scattering albedo increases with the increasing relative humidity, it is very close to 1 at relative humidity of 95%; within the thermal infrared band greater than 10 μm, the single scattering albedo decreases with the increasing relative humidity and it has strong ability to absorb radiation. The scattering intensity has less effect on relative humidity and shows a trend of decreasing firstly and then increasing with the increasing scattering angle, the increasing tendency decreases with the increasing wavelength; for the linear and circular polarization of scattered radiation, the change with the scattering angle and relative humidity has different properties at different bands; in the forward and backward scattering directions, it only produces the circular polarization by dust aerosol particles, when it is assumed that incident light is right hand circularly polarized. Polarization properties of scattered radiation and their differences with humidity mainly change in the backward scattering region, where it is as an arched form. The scattering angle for peak point is different at different relative humidities and the peak position drifts to the larger scattering angle with the decreasing relative humidity.