Abstract: As an important tributary of the Yangtze River, the protection and restoration of the water ecology of Daye Lake is of great practical significance to the Yangtze River Protection. Based on the water quality data of DO, COD_Mn, COD_Cr, NH₃-N, TN and TP in three conventional monitoring sections of Daye Lake from 2015 to 2020, the water quality was evaluated and the changing trend of water quality was analyzed. The problems of water ecological environment were discussed, and the remediation measures were put forward. The main conclusions were as follows: The water quality of Daye Lake was generally stable in the past six years, which was between Ⅳ to Ⅴ grade of Environmental Quality Standards for Surface Water (GB 3838-2002). The water body was in a state of mild eutrophication and had a gradual upward trend. TN and TP were the characteristic pollution factors of Daye Lake. The main reasons affecting the water quality of Daye Lake were the lack of lakeside buffer zone, the prominent non-point source pollution in agricultural and rural areas, the lag of sewage collection and treatment facilities in urban and rural areas, and the direct discharge of tailing water from domestic sewage treatment plants into the lake. The important work of ecological restoration and environmental treatment of Daye Lake in the future should include returning dikes to the lake, promoting the treatment of non-point source pollution in agricultural and rural areas, and improving the tailwater of the sewage treatment plant for deep purification of ecological wetlands.