Abstract: Water level fluctuations have a significant impact on the growth and development of aquatic plants in lakes. This study analyzes the water level data of Gucheng Lake from 2006 to 2023 and the aquatic plant variations from 2013 to 2021, investigating the relationship between aquatic plants' responses and water level changes. It proposes a sensitive ecological water level for gate-controlled lakes based on the restoration of aquatic plants. The findings show that: (1) The average water level of Gucheng Lake from 2006 to 2011 was 8.47 m; in 2012, a new inlet and outlet sluice was put into operation, increasing the post-flood storage water level from 8.50 m to 9.50 m. From 2012 to 2015, the average water level was 9.69 m. Since 2016, due to the influence of the Wushan Navigation Channel, the lake's water level fluctuated greatly within the year, with an average of 8.98 m from 2016 to 2023. (2) Between 2013 and 2021, the species diversity of aquatic plants in Gucheng Lake showed a decreasing trend; dominant species shifted from Potamogeton pectinatus, Potamogeton crispus, and Najas marina to Potamogeton pectinatus, leading to a gradual simplification of the aquatic plant community and a trend towards a transition from macrophyte-dominated to algae-dominated lakes. (3) The number of days with water levels exceeding 9.00 m in March–April and December–April was significantly negatively correlated (p≤0.05) with the biomass of aquatic plants in May. Maintaining higher water levels during the critical germination period of aquatic plants is a key factor contributing to the substantial decline in biomass. (4) The completion and operation of the Shuibi Bridge Pump Station in 2024 will provide objective conditions for further refining the water resource management of Gucheng Lake, and a preliminary sensitive ecological water level of 7.50 m is proposed for the germination of aquatic plants. During the sensitive period (March–April), the water level can be adjusted between 7.50 m and 8.50 m according to the plant germination status to balance water resource utilization and navigation requirements. It is recommended to strengthen aquatic ecological monitoring, further determine key restoration periods and priority areas for aquatic plants, and enhance the management of water conservancy projects to create favorable water level changes that support aquatic plant restoration, achieving a balanced approach to flood control, water supply, irrigation, ecology, and navigation