Some field experiments of aerosols had been carried out over the arid and semi-arid regions in China over the past 30 years,but there were little learning of the semi- arid region of Loess Plateau. Using Version 2.0 Level 2.0 dataset from the AERONET (Aerosol Robotic Network) Lanzhon_city site,the aerosol optical properties during dusty and non-dusty periods in winter and sprig when air pollrtion frequently occured most frequently were demonstrated. A comparison of the same parameters between Lanzhou and Beijing for spring was also analyzed. Some new information was gained concerning aerosol optical properties over the semi-arid region of Loess Plateau. The results show that the aerosol properties measured during dusty and non-dusty periods are significantly different at Lanzhon,particularly in spring,and also different from those at Beijing.