A new lake treatment concept is proposed for Dongting Lake based on the idea of central lake reservoir, which includes transforming lakes into reservoirs, waste water cleaning and diverting, flood storage and sewage discharge, and running water never becoming putrid. The impacts of the central lake reservoir construction in the West Dongting Lake on flood, water replenishment and water environment are numerically investigated by a two-dimensional hydrodynamic model, and the feasibility of its application is also discussed. The results show that the flood storage capacity of the central lake reservoir can greatly reduce the peak flood elevation in West Dongting Lake, reducing its flood control pressure. Water replenishment from the central lake reservoir in the dry season can also efficiently increase the water level in Kaihu channel to improve the navigation condition. Meanwhile, water replenishment from the central lake reservoir can greatly increase the flow velocity in Kaihu channel and Xiangjiang River downstream channel, resulting in enhanced water exchange and better water environment.