Abstract: Using the monthly precipitation data from 33 national meteorological stations in the Danjiangkou Basin, hydrological observations from the Danjiangkou Reservoir, and vegetation information from the benefit area of the Middle Route of the South-to-North Water Diversion Project collected between 2007 and 2022, the water-level change characteristics, influencing factors, and ecological effects over the recent 16 years were analyzed. The results revealed the following. (1) After the elevation of the Danjiangkou Dam, the annual average water level of the Danjiangkou Reservoir increased from 145.97 to 149.61 m. Although annual variability increased, seasonal variability decreased, indicating an improvement in the regulation and storage capacity. (2) By constructing a correlation model between the Danjiangkou Reservoir water level change in the next month and the surface rainfall in the current month, the monthly water level predictions could be made, which provided the decision-making basis for the flood discharge or water transfer plan of the reservoir. (3) After constructing the Middle Route of the South-to-North Water Diversion Project, the fractional vegetation cover in the benefit area increased from 75.5% to 76.1% in August, among which areas with small population densities increased locally by ＞20%.