To prevent and reduce the occurrence of WUI fires, this study mines the key causal factors of WUI fires and clarifies the action mechanism between the causal factors. First, this study obtains the causal factors from WUI fire accident cases based on the proposed mining technology and uses the Apriori algorithm to obtain association rules between the causal factors. Then it uses the complex network theory to construct the WUI fire causal factor network, calculate the topological parameters of the network, and analyze the characteristics of the WUI fire causal network. Finally, the study introduces the risk index of the WUI fire causal chain, mines the high-risk connecting edges, and proposes the chain breaking measures. The results show that the WUI fire causal factor network has a small-world characteristic, and high temperature, strong wind, and drought have a greater influence on other causal factors. Burning waste, plant fire, emergency response speed, human arson, and strong wind have important roles in the conversion of different causal factors, which should be controlled better. The most risky side of the network is burning waste → plant fire, and the risk chain can be cut off by enacting regulations such as the prohibition of unauthorized burning waste, to achieve the prevention and active control of WUI fires.