Abstract: Continuous monitoring of precipitation had been carried out in Xiamen area from 1992 to 1994. The results show that the rainwater in Xiamen area is acidified, the year average pH range is from 4.48 to 5.09, and the frequency of acid rain is from 46% to 92%; the seasonal variation of rainwater acidity is obvious, and the degree order (from high to low) is spring, winter, summer and autumn; the main anion in rainwater is SO^2-₄, which means that acid rain in Xiamen area is sulfur acid type; there is a more serious tendency of rainwater acidity year by year.