According to the data of acid rains in 7 stations over Hangzhou from July 2009 to June 2012 and their relationships with the atmosphere composition, analyses are made of the trend and distribution characteristics of acid rains in Hangzhou during the recent three years, and the different meteorological conditions and the influence of air pollutant on acid rains are investigated. The result reveals that the average pH of precipitation is between 437 and 523 during recent three years; the degree of acid rain pollution is more serious in the west part and less serious in the east of Hangzhou;the precipitation acidity and the frequency of acid rain show a small fluctuation, but the trend is not obvious in general; the pollution level of acid rains is lowest in summer, highest in autumn and winter, and moderate in spring. The relationship between precipitation intensity and pH and K varies from one station to the other: there is a positive relationship between precipitation intensity and pH in the stations of Linan, Chunan, Jiande, and Fuyang, and the relationship between precipitation intensity and pH in stations of Hangzhou and Tonglu is not obvious.Particularly, there is a negative relationship between conductivity and precipitation intensity for all stations. Under the influence of the north wind at 850 hPa, the precipitation acidity is more severe and the conductivity is higher. The pH of precipitation is positively related to the height of the inverse temperature at lower levels and negatively related to the thickness of the inverse temperature. Severe haze weather always accompanies the strong acid rains during the early half stage of the precipitation. The relationship between inverse temperature and conductivity of precipitation is not obvious. There is a significant negative correlation between the concentration of atmospheric pollutants, such as SO2, NO2 and PM25, and the pH of rain water, suggesting that the variation of pollutant concentration in the lower atmosphere layer has significant influence on acid rains.