Using the large-scale multiple reservoirs upstream of the Lutaizi section in the Huaihe River Basin as an example, the flood hydrographs of downstream sections before and after construction of reservoirs were compared, and the total impact of multiple reservoirs on the flood hydrograph was analyzed. An approach that adds reservoirs one by one was used to determine the contribution of each reservoir to the change in the flood hydrograph, and the degree of influence of each reservoir was determined. The hierarchical clustering method was used to determine the degree of influence of reservoirs, and the highly important reservoirs were picked out. The results show that large-scale multiple reservoirs in the Huaihe River Basin significantly reduces the flood volume and flood peak of the Lutaizi section, and the time of the peak is changed. The impacts of each of the reservoirs on the flood hydrograph are different. The Meishan, Xianghongdian, Suyahu, Nanwan, Nianyushan, and Foziling reservoirs have significant influences on the flood hydrograph of the Lutaizi section, and are important to flood control decisions in the Huaihe River Basin.