Using the continuous data of PM2.5 mass concentration, aerosol absorbing and scattering coefficients collected during March and May 2006 at the Shangdianzi background station, a primary study of the optical properties of aerosol in sanddust weather is conducted. The results indicate: (1) In the selected clear days, the value of PM2.5 mass concentration and daily average absorbing and scattering coefficients were about 10 μg/m3, 7 Mm-1, 20 Mm-1, respectively. The value of singlescattering albedo ranged from 0.71 to 0.78. During the transportation of pollutants from urban area to the background station, the average PM2.5 mass concentration, absorbing and scattering coefficients were 145 μg/m3,445 Mm-1, and 374.3 Mm-1. The value of single scattering albedo ranged from 0.84 to 0.94.While in sanddust weather, the value of PM2.5 mass concentration, aerosol absorbing and scattering coefficients, single scattering albedo ranged from 248.2 μg/m3to 424.1 μg/m3, 10.8 Mm-1 to 44.7 Mm-1, 225.4 Mm-1 to 393.9 Mm-1, and 0.89 to 0.96, respectively. (2) Affected by the sanddust weather, the increasing ranges of aerosol mass concentration and scattering coefficients were much greater than that of absorbing coefficient. (3) Through comparing the results from the three kinds of weather, it is found that the sanddust weather made the concentration of particles increase up to an abnormally high value and fluctuate greatly in a short time. The absorbing coefficient of aerosol in sanddust weather was much higher than in clear days but lower than during the pollutant transporting process from urban area to background station. The scattering coefficient of aerosol in sanddust weather was much higher than in clear days, close to that during the pollution case. The sanddust weather contributed to the scattering effect more greatly than to the absorbing effect of aerosol.