In-situ measurements of aerosol optical properties were conducted at Mr.Huang from September 23 to October 28,2012.Low averages of 82.2,10.9,and 14.1 Mm-1 for scattering coefficient (σsp,neph,550),hemispheric backscattering coefficient (σhbsp,neph,550),and absorption coefficient (σap,550),respectively,were obtained.Atmospheric aging process resulted in the increase of σap,550 but the decrease of the single scattering albedo (ω550) at constant aerosol concentration.However,the proportion of non-light-absorbing compo nents (non-BCs) was getting higher during the aging process,resulting in the increase of aerosol diameter,which also contributed to relatively higher σsp,neph,550 and ω550.Diumal cycles of σsp,neph,550 and σap,550 with high values in the moming and low values in the aftoon were observed closely related to the development of the planetary boundary layer and the mountain-valley breeze.BC mixing state,represented by the volume fraction of extally mixed BC to total BC (r),was retrieved by using the modified Mie model The results showed r reduced from about 70％ to 50％ when the extally mixed non-BCs were considered.The periodical change and different diumal pattems of r were due to the atmospheric aging and different air sources under different synoptic systems.Local biomass bing emissions were also one of the influencing factors on r.Aerosol radiative forcing for different mixing state were evaluated by a two-layer-single-wavelength model,showing the cooling effect of aerosols weakened with BC mixing state changing from extal to core-shell mixture.