By using the ground-based observation retrieval data from CE318 sun-photometer in Nanjing of 2003, the variation characteristics of aerosol optical properties were analyzed. Moreover, the graphical method was used to analyze the aerosol type classification. Results show that the maximum of the Aerosol Optical Depth (AOD) in Nanjing occurred in January (0.97±0.49), the minimum one appeared in July (0.53±0.37), and the annual mean value was 0.71±0.42; except March, the value of Ångström exponent α was 0.8 higher in the rest months, and the maximum value appeared in August and December(1.24±0.17); the seasonal mean value of AOD in winter (0.85±0.47) and spring (0.72±0.45) were slightly higher than that in summer (0.63±0.40) and autumn (0.62±0.36), and the seasonal mean value of α were as follows: winter (1.18±0.16) > summer(1.15±0.32) > autumn (1.05±0.33) > spring (0.86±0.21). The diurnal variation of AOD presented high value in the morning and evening and relatively stable during the day, however, a single peak existed in winter, which appeared at 13∶00 with the value of 1.05±0.64. Industrial and urban composite pollution caused by fine particle pollution accounted for a relatively high proportion. The most frequent distribution of AOD and α with the peak center at 0.53 and 1.2 accounted for 21% and 16%. The AOD high value area(>0.7) in Nanjing data mainly centered in the fine mode growth part(1.0 < α < 1.4, δα<0,η~70%),and aerosol fine mode size ranged from 0.10 to 0.15 μm.