The discharge structure is an important part of the reservoir hub, which is an important factor affecting the selection of charateristic water level of dams and the flood control safety of the reservoir, and the selection of flood discharge mode and flood regulation calculation are the design focus of discharge structure.In order to solve the problem of insufficient water intake in the branch ditch where the reservoir hub is located, Ziwei reservoir adopts the arrangement of combining the main dam and the secondary dam, and the water volume of the main ditch where the secondary dam is located is diverted to the main dam for replenishment through the connecting tunnel in the reservoir area.In view of the geological conditions and engineering investment restrictions, the main dam does not have flood discharge facilities, and the method of flood discharge of the main dam is proposed to use the connecting tunnel in the reservoir area to drain from the overflow dam of the secondary dam, the layout form of outlet structure of the reservoir hub is introduced, and the calculation method of the joint flood regulation of the main dam and the sub-dam of the Ziwei reservoir hub is proposed, which can provide reference for the engineering layout and flood control calculation of flood discharge buildings in small and medium-sized reservoirs.