In order to effectively solve the problems of equipment, the fault tree analysis method is used to analyze the crank fracture fault of the locker locking mechanism that appears in the commission. Find the cause of the failure, draw a fault tree, and find out the logical relationship between the causes of the failure. Through qualitative analysis and quantitative calculation, the minimum cut set of the fault tree is determined, the probability of occurrence of the top event and the probability of occurrence of each cut set are calculated, and the influence degree of each cause fault is analyzed. This research can provide a basis for efficient troubleshooting.