Earth-observing satellites have provided satellite image datasets for urban-scale air quality monitoring. Aerosol optical depths (AOD) at 1 km resolution is retrieved from MODIS on Terra and Aqua Satellite by using the improved algorithm. The 1 km AOD data are validated by using AOD measurements of AERONET station in the period from September 2013 to January 2014. Then the validated 1 km AOD data are compared with ground-based PM2.5 mass concentration and PM10 mass concentration in Nanjing metropolitan area respectively. Then these models have been amended by fine aerosol optical depths and the meteorological factors. The revised model of Nanjing metropolitan area is y=136.78+9.16x1-0.36x2-3.98x3, with R2=0.79. By applying the model, it is confirmed that the aerosol optical depths can be used to evaluate the quality of urban air.