As one of the important disaster prevention and mitigation facilities, reservoir can regulate flood and reduce the flow of downstream river by storing flood. In order to fully tap the flood control potential of the reservoir and improve the flood control capacity of the reservoir, this study takes the Waterfall Reservoir as an example, through tapping its potential in the aspects of gate transformation, flood holding capacity, operation conditions, etc., and puts forward the optimization scheme of flood sluice and operation mode. On this basis, combined with the principle of compensation regulation, the flood process and its change trend, the reduction of peak flow and the delay of peak time are analysed systematically. The results show that after reservoir regulation, the maximum overflow capacity of the river is the designed peak flow of the interval under the condition of 20 to 50 years of flood, and the downstream river is flowed according to the safe flow under the condition of 20 years of flood, the flood containment capacity of the reservoir is greatly strengthened, and the flood storage capacity of the downstream river is significantly improved. The research can provide reference for the rational operation of reservoir flood, reservoir planning and design and watershed planning.