Abstract: Ecological construction for regional sustainable development is mainly by increasing ecological carrying capacity.However,most ecological evaluation studies today focus on economic,social and ecological aspects,very much lacking on the carrying capacity of ecosystems.Such is a hindrance to efforts in weighing results of ecological construction.This paper evaluates the effects of “re-submerging polder” policy on the ecological carrying capacity of Dongting Lake.Introducing ecological carrying capacity theory to a flood prone region is the basis of the evaluation.Thus the paper broadens the scope of application of ecological carrying capacity theory.Finally,the paper suggests important points for sustainable development in the Dongting Lake area.