An observation experiment of aerosol optical characteristics was carried out with automatic sun tracking photometer CE-318 in November, 2007. The theory and methods of aerosol optical depth(AOD) retrieving are discussed in detail. The CE-318 was calibrated using Langley method. AOD and Angstrom parameters were retrieved based on the obtained data. The average AOD is 0.5183 at 550 nm, and the average Angstrom parameters [EQUATION] and [EQUATION] are 0.2325 and 1.3373, respectively. The daily variation of AOD and the cause are discussed. The results show that small particles are primary in Xianlin region, Nanjing, and it is important for analyzing and monitoring air pollution and improving air quality of Nanjing.