Reservoir flood control and routing are essential in the design of small-scale reservoirs. This paper is based on the five point waist folded triangular flood hydrograph calculated in the 2010 edition of the rainstorm and Flood Checking Manual in Jiangxi Province, combined with the simplified triangle method for analysis. Based on the analysis of the inflow process line of the five point folded triangle in Jiangxi province, the maximumdischarge capacity of the reservoir under different operating conditions can be obtained byusing the difference between inflow and outflow as the principle of storage capacity, the relationship between reservoir water level and storage capacity, and the relationship between water level and outflow, according to the total amount of surface floods and the peak flow rate of surface floods.Combining a large number of engineering examples, it shows that in order to control the error within -8% to +8%, on the one hand, this method is applicable under the assumption that the duration of the discharge flow process t is equal to the duration of the upstream reservoir flood T. On the other hand, when selecting the final results, it is necessary to simplify the calculation value of the flood control results to be greater than 0.4 times of the surface peak flow value.