Abstract: Based on the data of water transparency and its main influencing factors in Fuxian Lake over the years,this paper analyzed the changes of water quality and its environmental risks, and the countermeasures were put forward. The results showed that the number of planktonic algae in Fuxian Lake has increased significantly from 1980s to 2002. During this period, the concentration of chlorophyll-a in the water also has increased significantly from 1990 to 2020, and the water transparency decreased rapidly. The water transparency was mainly affected by planktonic algae and chlorophyll-a. With the advancement of water pollution control and water ecological restoration in the lake, the dissolved organic pollutants in the water of Fuxian Lake have decreased steadily in the past ten years, and the transparency of the water has become stabilized, and the transparency has been significantly affected by rainfall. The control and maintenance of the lake is a long-term process. In order to contain the eutrophication trend of Fuxian Lake and to stabilize and improve the transparency of the water body, the water ecological environment protection and comprehensive management of the whole watershed need to be carried out continuously and comprehensively.