The Event tree model for failure of city gas pipeline is established in this article according to the property of city gas,the fault tree analyses are incorporated into the event tree. The fault trees are used to analyze the causes and probabilities of the initial event and subsequent events, while the event tree is used to analyze the subsequent event of gas leaking and the probabilities of the consequential events. Thus, a comprehensive analysis method for failure of city gas pipeline and its hazard has been produced.