To clarify the role of the emergency organization in breaking the disaster chain during the execution of emergency tasks and describe the evolution process of the collaborative network, taking the Shulan rainstorm in 2023 as an example, emergency task was regarded as the bridge connecting the disaster event and the emergency organization. The topological structure of the rainstorm disaster chain network and emergency organization network was analyzed. The effect of collaborative network was measured by taking the total amount of vulnerability reduction at the edges of the disaster network controlled by emergency organizations at each stage during the execution of tasks as the standard. The results indicate that disaster events caused by heavy rain exhibit high clustering effects, significant mutual influence, and short disaster paths. In the emergency organization network, most highly centralized organizations are government entities, which have strong capabilities to directly interact with other nodes. By contrast, organizations with low centrality, primarily enterprises and social organizations, tend to be more independent from other nodes. Each emergency organization can coordinate and control critical disaster events and disaster chains with greater vulnerability. In the stage of clearing and resettlement, the number of emergency tasks, disaster-response organizations, and broken chains is the highest, and the total amount of edge vulnerability reduction is also the greatest. By contrast, during the stages of emergency rescue, recovery and reconstruction, early warning and response phases, edge vulnerability reduction decreases sequentially.