Samples of zooplankton were collected for 4 times from May, 1989 to May, 1992 in some suburban waterbodies of Chongqing City, a heavy acid rain area in the southwest China. The qualitative and quantitative analysis results indicated that the species of zooplankton (y) were found to decline gradually with a reduction of pH value (x) ranging from 4. 01 to 8. 80. The regression equation of relation between them may be expressed as: y = 1.520x-2.488 (r = 0. 61, P lt 0.01, n = 22) with respect to abundance of zooplankton, the mean density was abundant (3609. 23 ind./L) at pH ranging from 5.0 to 8.8 , but was lower (151.50 ind./L) at pH ranging from 4.0 to 5.0. The evidence presented suggests that effects of low pH on zooplankton is the greatest below pH 5.0.