The outbreak of Yantze vole (Microtus fortis) population in Dongting Lake region is closely related to the evolvement of lake beaches, because the deposition of lake sediments results in the expansion of lake beaches, which provides the possibility of the increase of the vole's population. Reclaiming farmland from lake via building cofferdams, eliminating snails by building cofferdams for eradicating schistosomiasis, and over-hunting predators in the region cause the voles becoming a pest after the 1970s. In recent years, the Three Gorges Project and the conversion from farmland into lake have had deep impacts on the environment in the Lake region. The dispatching of the down flow rate by the Project induces the expansion of the low and medium level beaches in the Lake region, while converting farmland into lake directly induces the increase of beach area, both of which expand the potential habitats of the vole's population. Therefore, more attention should be paid on the quantitative variation trend of the vole's population in the future.