Abstract: This study collected hydrological data from 1953 to 2024,water quality monitoring data from 2018 to 2024,and algae survey data from 2021 and systematically studied the ecological and environmental effects of continuous water level decline using Pearson correlation analysis and nutritional status index evaluation.The results showed that before 2008,the water level and quality remained generally stable,but over the next 16 years,the water level continued to decline,with an average annual decrease of 0.22 m（1723.05 m→1719.56 m）,resulting in a reduction of 2.91 km² in lake area and a decrease of 660 million m³ of water storage capacity.The ecological impact presented a chain reaction.The drop in water level directly damaged the vegetation in the 2.51km² lakeside zone,leading to the loss of biological habitats in the area.Correlation analysis showed a significant negative correlation between water level and total phosphorus （TP）(r=-0.363**,P<0.01),while TP was positively correlated with chlorophyll-a（r=0.258*,P<0.05）.The comprehensive nutritional status index increased to 22.9,3.4 times that of the 1980s,and the degree of eutrophication in the water body accelerated.Suggestions on implementing ecological water level control （≥1721.8 m）,controlling pollution sources and restoring ecological system were put forward to maintaining the balanced lake ecological system.