According to ever increasing the utilization of floodwater and in combination with flood regulation, the flood control water level of Danjiangkou Reservior per ten day mean during flood season was statistically analysed by using the relative frequency theory and combining flood regulation. For taking ten day as control time interval of reservoir stage flood control water level, the Danjiangkou Reservoir can greatly improve economic benefit, without increasing risk of flood control standards during flood period and the post flood season.