Taking MOD13Q1(vegetation indices 16-day L3 globe 250m) dataset, which is a data production composited by Terra/MODIS of 11 years as a main data source of Lake Dongting, the water surface area of Lake Dongting were extracted by setting threshold values on NDVI(Normalized Difference Vegetation Index) and NIR(Near InfraRed). Under the background of the Three Gorges Project, combined with the data of water area and water level, the paper analyzed the interannual variation features and the variation rule within a year of water area in Lake Dongting, and deeply explored the quantitative relationship between water level and water surface area by integrating with water level data of Chenglingji hydrological station. The result indicated that the Three Gorges Project largely controls the water yield from the Yangtze River into Lake Dongting; Under the effects of climate change and the operation of Three Gorges Project, Lake Dongting area has a decreasing trend on the whole; The fitting result indicates that water surface area has good correlation with water level and the deterministic coefficient of the fitting curves was 0.975 from 2000 to 2003.