Prefabricated utility tunnel plays an important role in the modern urban infrastructure construction. However, the weight of prefabricated utility tunnel segment is heavy and the hoisting conditions are complicated, which puts forward higher requirements on the reliability of the main equipments for the erection and paving of the utility tunnel, especially the hydraulic system of the tunnel erecting machine. Therefore, the reliability analysis of the hydraulic system of the tunnel erecting machine is carried out in this paper. Firstly, the working principle of the tunnel erecting machine and hydraulic system is analyzed, and the T-S dynamic fault tree model is constructed by using the T-S dynamic fault tree analysis method, and it is transformed into a Bayesian network model. Secondly, according to the failure probability of the root node, combined with the Bayesian network conditional probability table, the failure probability of the leaf nodes of the hydraulic system of the tunnel erecting machine in each time period and task time is forwardly inferred. Then, through the quantitative analysis of the probability importance, key importance and sensitivity parameters in the Bayesian network analysis method, the importance of the components in the system can be reflected. Finally, the posterior probability of the root node of hydraulic system fails is calculated through the reverse reasoning of the Bayesian network analysis method, and the sensitive components of the system are found. The results show that the proposed method can find out the main reasons that affect the hydraulic system of the tunnel erecting machine, and provide reference for the safe operation of the equipment and system maintenance.