Abstract: With the complex refractive index data of sulfate and soot aerosols, the radiative property of the aerosol under 8 different relative humidity conditions was calculat ed in this paper. By using the concentration distribut ion (from two CTM models) and LASG GOALS/AGCM, the radiative forcing due to hygroscopic sulfate aerosol was simulated. The results showed that:(1) with t he increase of relative humidity, the mass extinction efficiency fact or decreased in the short wave spectrum; single scatt ering albedo kept unchanged except for small increase in long wave spectrum, and asy mmetry fact or increased in whole spectrum; (2) larger differences occurred in radiative forcing simulated by using two CTMs data, and the global mean forcing simulated were-0.268 and-0.816 W/m2, respectively; and (3) when the impact of relative humidity on radiative property was taken into account, the distribution patt erns of radiative forcing simulated were very similar to that of dry sulfate property, but the forcing value decreased by 6%.