In order to alleviate the flood disaster caused by urban rainstorms and find the weak links affecting the vulnerability of existing storm sewer sections, the concepts of vulnerability of urban storm sewer system and storm sewer sections are introduced, the influencing factors of vulnerability of existing storm sewer sections are summarized, and the correlation degree of each functional module is analyzed comprehensively. Based on the complex network topology model, a method is proposed to determine the vulnerability of existing storm sewer sections by the node important degree. The results show that the method can reflect the difference of importance between nodes, make the judgment of node vulnerability more accurate, and provide a theoretical basis for the subsequent reconstruction and construction of urban storm sewer system. It can provide early warning of accident section for intelligent drainage pipe network system, which is one of the important branches of sponge city construction, and improve the efficiency of emergency repair and maintenance services.