This paper sampled the data according to the theory of partial duration series, and used the Copula function to establishthe joint distribution between the magnitude and occurrence time of the flood peak, the quantity of flood during 3 days and 7days. As a result, the probability distribution of the flood occurrence time was obtained at the various magnitudes, which is usefulfor reservoir regulation in flood control. At the same time, Copula function was used to establish joint distribution of the annualmaximum flood peak, 3-day and 7-day flood quantities, so as to get floods the design standard and check standard. And then thedesign flood hydrograph was obtained by using the method of homogenous frequency enlargement. The flood hydrograph is better inthe way of the inherent law of hydrological phenomena. It shows a nice prospect in the field of hydrological flood frequency analy -sis and calculation of the theory of partial duration series and Copula function.