The radiation properties of soot-sulfate aerosol are analyzed in a mixed state using Mie theory, external mixture model, uniform sphere model and the concentrically coated sphere model. Meanwhile, the influence of mixture method, volume content and particle size on the radiation properties mentioned above is discussed further. The results show that single scattering albedo and absorption efficiency factor are substantial sensitive to soot content and mixing patterns, and asymmetry factor and scattering efficiency factor are weak to the both, while extinction coefficient (extinction efficiency factor) are not sensitive to the both. The absorption of uniform mixture of soot-sulfate aerosol is the strongest, and then the coated sphere model. Among the three models, external mixture model is the lowest. In the coated sphere model, the absorption of soot coated with sulfate is larger than sulfate coated with soot. Radiation properties of small particle are substantial sensitive to the change of particle size, while the large particle is not quite.