On June 19th, the Beijiang River Basin was afflicted by the “No.2 Flood in 2022” which is the largest flood in this basin since 1915. In order to understand the characteristics of rainstorm flood in the Beijiang River Basin, a comprehensive study was conducted using a combined qualitative and quantitative approach. The characteristics of rainstorm center, flood magnitude and flood propagation speed were analyzed and compared with historical rainstorm flood events. With the method of the seed spread algorithm, the regulation effects of “ideal drainage control” and “experience drainage control” scheduling schemes were compared. The study also took into account the dynamic reservoir storage capacity when simulating flood control scenarios. The results show that the main causes of the flood disaster included extensive cumulative rainfall, high-intensity precipitation, and the concentration of the storm’s impact area. It was observed that Feilaixia Reservoir had achieved remarkable results according to the “ideal drainage control” rule. However, it was highlighted that the influence of dynamic reservoir storage capacity must be considered in flood control operation. The research results can provide a technical support for the flood control, disaster mitigation and formulation of regulation rules in the Beijiang River Basin.