In order to study the problem of oil leakage in subsea Xtree system and prevent the occurrence of major safety accidents,the Bayesian model of subsea XTree system leakage was established combining the fault tree and Bayesian network.Combining the prior data with Bayesian theory,the probability distribution of system failure,as well as the importance factor of each event were calculated,and the weak parts of the system were found out,the risk analysis of subsea XTree system leakage accident was realized.The results show that the fault tree model and Bayesian method can effectively overcome the limitations of the traditional fault tree analysis method,and the analysis results are in good agreement with the historical statistical experience,which proves the feasibility of the Bayesian network method in evaluating the leakage risk analysis of the tree system.