In order to determine the lowest ecological water level in the Dongting Lake area, the complexity of the Dongting Lake area and the great differences between different lake areas were studied. Based on the hydrological data of five hydrological stations, Chenglingji, Lujiao, Nanzui, Xiaohezui and Yangliutan, from 1953 to 2013, the natural water level data method, annual guarantee rate method, minimum annual average water level method, ecological water level method, lake morphology analysis method and minimum spatial demand were adopted. The lowest ecological water levels of East Dongting Lake, South Dongting Lake and West Dongting Lake were calculated, and compared with the previous research results on ecological water levels of Dongting Lake. The results show that the lowest ecological water levels of East Dongting Lake, South Dongting Lake and West Dongting Lake are 22.62m, 27.19m and 28.11m, respectively, and the corresponding lake surface areas are 373.85km², 406.88km² and 142.19km², respectively. From the point of view of protecting the Dongting Lake Nature Reserve, the lowest water level determined is reasonable.