Erhai Lake is located in the west of Yunnan Province. It plays an important role in the Dali regional economic development. However, with the development of economy and increase of population in the region, the impacts of human activity on ecological environment of Erhai Lake have been strengthened. Based on the investigations on Erhai Lake from 1996 to 1997 and data of the past 40 years' research, this paper gives a detailed analysis on the succession of its aquatic communities. From 1957 to 1997, the density and biomass of phytoplankton increased nearly 10 times and this change was more intensive in the last 15 years. The dominant species have also changed greatly. The non-pollution resistant species such as Ceratium hanclelli Skuja, Psephone-ma aenigmaticum Skuja, Lyngbya Limnetica Lemm. have disappeared, while the species which can indicate eutrophication such as Anabaena spiroides Klebahn and Microcystis fios-equae (Wit-tr.) Kirch increased. Because of the transformation of “Four Domestic Fishes” and ice fish, the density and biomass of zooplankton have been decreasing.However, organic pollution resulted in the rise of density and biomass of limnitic oligochaeta and chironomid larvae. The density of zoobenthos has increased nearly 8 times. There are two apparent variation periods of aquatic vegetation. From 1957 to 1985, distribution of aquatic vegetation tended to expand. From 1985 to 1997, it tended to reduce because of unreasonable utilization. With the transformation of extra fishes, rapid decrease of water level, over capture of fish resources etc., the fish community of Erhai Lake has changed greatly. In the 1950s and 1960s, the fish community was dominated by aboriginal fishes. In the 1970s, the fish Ctenogobius cliffordpopei was dominant. In the 1980s, the dominated fish turned to Carassium auratus.In the 1990s, the ice fish and common carp become main economic fish of Erhai Lake.fishes tend to die out. The fish of Schizothorax taliensis has disappeared.