The temporal and spatial distribution of precipitation acidity is analyzed based on 1983—1985 data from the ten environmental monitoring stations of Nanjing. The pH of acidity averages 5.09. The frequency of acid rainfall with pH less than 5.60 is 42%. The acidity is increasing gradually, higher in the city proper than in its suburbs, and the lowest in its surrounding counties. Analysis indicates that there is some correlation between Nanjing precipitation acidity and atmospheric pollution.