The purpose of this paper was to study the vegetation cover and water level change functions of East Dongting Lake wetland. The vegetation cover corresponding to water level change was also investigated. After the preliminary treatment of TIMESAT, the normalized difference vegetation index (NDVI) time series was adopted to analyze the relationship between vegetation cover and water level in the divided zones (A, B, and C). Then, NDVI sample autocorrelation curve was used to show the differences of the three areas under study. Lastly, the spearman correlation coefficient (ρs) of NDVI time series corresponding to water level was used to discuss the effects of the Three Gorges Dam. The results indicated that, (1) all the NDVI time series under the impacts of water level formed an annual cyclical change style. Every cycle had two crests, one in April and the other in October. In the flood period, the curve formed a trough in July. Quadratic polynomial fitting showed that the critical water level of maximum vegetation cover was about 24 25m. (2) The degree of the effects of water level on vegetation cover was Zone A