Based on the two-dimensional flow model and by applying the finite volume method and unstructured mesh, the waterlogging and drainage of the Datong Lake Region, heartland of the Dongting Lake Plain under various rainstorms were studied. The spatial distribution of waterlogging in the Datong Lake Region and the ratio of waterlogging were obtained. The negative influences of the increased intensity of the rainstorms on the waterlogging were analyzed quantitatively. The results of the research can provide technological support to the waterlogging forecasting and assessment.