Abstract: As a key parameter of multi-purpose reservoir operation,flood limit water level plays a critical role in achieving the balance between flood control and economic benefit such as hydro-power generation and navigation improvement etc.The currently adopted flood limit water level pays too much attention to the floods of low probability,thus reducing the economic benefit of the reservoir during the flood period.It is theoretically and applicably essential to adopt a dynamic flood limit water level in the operation.According to the general operation rules of Three Gorges Reservoir(TGR),a real-time model under dynamic flood limit water level is developed and used to simulate the TGR operation by using the daily river flow series of the Yichang gauging station about 40 km downstream to the dam site of the TGR during the period of 1882-2001.The multi-objective criteria and a comprehensive evaluation model are proposed and developed to measure and assess the TGR operation risks.The optimum scheme is obtained by comparing nine alternatives of dynamic flood limit water level schemes.