Abstract: There are a variety of municipal pipelines in the underground utility tunnel, and once an accident occurs, the property loss and social impact will be huge. Disaster prevention and reduction can be achieved by accurately evaluating the impact value of disasters in the operation stage of utility tunnel and quantitatively analyzing the impact range and degree of disasters. This paper analyzes the evolution process of the internal and external disaster-causing factors and the disaster evolution path in the operation stage, and establishes a disaster evaluation model based on graph theory and AHP method. Taking Tongzhou section A utility tunnel project as the background, the model was used to obtain the impact values of each disaster in the utility tunnel and determine the disaster chain that needs to be managed. The research shows that the major factors affecting the disaster value of Tongzhou section A utility tunnel are explosions, earthquakes, quality problems and design problems. A chain-broken disaster reduction in terms of hazard factors, disaster-pregnant environment and disaster-bearing bodies is proposed. The research results can provide reference for disaster prevention and reduction of utility tunnel.