The construction of urban underground comprehensive pipe gallery often passes through environmentally sensitive areas. The accident tree is used to analyze the construction risks in environmentally sensitive areas, and a logical relationship tree between the overhead events and the causes of the accidents is established to qualitatively and quantitatively analyze the potential risks of construction in environmentally sensitive areas. From the calculation results of the minimum diameter set of the accident tree, it can be seen that the two basic events, construction qualification and construction sequence, have the greatest structural importance, which indicates that the construction qualification is not up to standard and the construction sequence is wrong are the two factors to be considered in preventing accidents.