Abstract: The traditional design flood estimation method assumes that the flood peak and the flood volume are at the same frequency,without considering the correlation between the two flood characteristics. Furthermore,when the design flood region composition under a specific return period is estimated,although the traditional method is from the most unfavorable point of view,it is impossible to quantitatively describe the correlation between the floods in each subarea. Therefore,in this paper,Copula function is used to deduce the design flood peak and flood volume at different frequencies which consider the combined effects of flood peak and flood volume,and then obtains the design flood process at different frequencies. The marginal distribution of flood components in each area is established and the most suitable Copula function between components in each area and design section is preferred which consider the spatial correlation between each flood zone and Huayuankou section,and then explore the most likely design flood region composition. It shows that the design results obtained by considering the correlation between flood elements in this study are slightly higher than those deduced by traditional methods under the same return period. The method in this paper can qualitatively and quantitatively describe the design flood region composition in the study area so as to obtain the design flood results that consider both the correlation of flood characteristics and spatial correlation at the same time,which are more objective and more consistent with the actual situation of design flood region composition in the basin.