By using the acid rain observation data during the Meiyu period from 2008 to 2014, the precipitation and the air pollutant data during 16-27 June 2014, the characteristics of the acid rain in recent 7 years and the scavenging effect of the changes of the air pollutant, pH value, K value and the orecipitation on the pollutant were analyzed. Results show that the average pH value of acid rain during the Meiyu period increased yearly in Wuxi. The concentration of air pollutants in the precipitation process significantly decreased, which was affected more by its durnal variation and emission source than by rainfall. The pH and K value were inconsistent during each precipitation. The K value was consistent with the particulate concentration. The effects of precipitation and wind on the particulate matter concentration was greater than that on gas. There is a limit of removal effect on particulate matter for long-time precipitation. When the hourly precipitation was between 0 mm and 0.5 mm, the scavenging effect was negative. When the hourly precipitation was between 0.6 mm and 5.0 mm, the scavenging effect was positive. When the hourly precipitation was more than 5.0 mm, the scavenging effect on PM2.5 and PM2.5-10 was positive, but for PM10, it was negative. Precipitation has a dilution effect on SO₂.The dilution effect on NO₂ depends on its starting concentration, and the removal effect is not significant on CO and O₃.