Water eutrophication has become one of the most serious problems in Chaohu Lake problem in recent years, and understanding the mechanisms of water eutrophication in Western Chaohu Lake will help for prevention and remediation of water eutrophication. In this paper, we selected 6 routine sampling sites in the water area of Chaohu Lake. TP, TN, CODMn and Chl-a are chosen to describe the eutrophication of the Study area. The influencing factors and major mechanisms of water eutrophication were discussed. The reasons of eutrophication changes in Western Chaohu Lake are very complicated; consist of the suitable natural condition, the built of Yuxi Gate, the deteriorated watershed ecological environment and a great amount of pollutants discharged. The treatment and control of the industrial and domestic wastewater from Hefei City are essential to the treatment. More attention should be paid to the treatment of non-point pollution.