Tailings ponds are mostly located in mountainous areas with scarce hydrological data, and the rational formula method is widely adopted for their design flood derivation, in which the determination of the confluence parameter m value directly affects the engineering scale, safety and reliability, and economic benefits. However, in actual engineering design and safety evaluation, the determination of the m value has often not received enough attention, leading to deviations in calculation results and affecting the rationality and safety of the project. Confluence parameters not only depend on natural conditions such as the underlying surface of the basin, but also have a dynamic coupling relationship and nonlinear feedback effect with elements such as peak discharge and confluence duration. According to the Regulation for calculating design flood of water resources and hydropower projects and the Hydrological Manual of Qinghai Province, the m value ranges were determined respectively, and the response laws of confluence time, peak discharge, and average flow velocity to the variation of the m value were systematically investigated. The results shows that the confluence parameter has a significant regulatory effect on peak flood discharge, and this response mechanism has not received sufficient attention. Given that the catchment areas of tailings ponds are mostly small-scale watersheds, it is recommended to scientifically determine the m value based on systematic analysis of topographic and geomorphological characteristics, vegetation coverage characteristics, and field investigations, following the concept of "localized adaptation and multidimensional verification", so as to improve the scientificity and reliability for the design and construction of tailings ponds.