The dynamic control bound of flood limited water level (FLWL) is a fundamental and key element for implementing reservoir FLWL dynamic control. The acceptable risk constraints and quantificational analysis of flood control operation were proposed by considering the most important risk sources, i.e., reservoir inflow forecasting error and uncertainty of flood hydrograph shape. The inflow uncertainty, risk analysis and the process of dynamic control bound determination were incorporated organically, and a dynamic control bound of reservoir FLWL was calculated using forecasting pre-release and Monte-Carlo simulation methods. The application results of the Three Gorges Reservoir (TGR) showed that the dynamic control of FLWL can effectively increase middle and small flood water resources utilization rate without increasing flood control risk. The TGR could generate 6.99×108~14.45×108 kW·h extra hydropower energy during flood season by using 1~3 day inflow forecasting information. The proposed methods can also be applied to other reservoirs.