Abstract: Fault tree analysis is an effective way to analyze the safety and reliability of complex system. Using this method, this paper discusses the failure of pipelines. The fault tree of oil and gas pipelines is established by considering two major failure modes of pipelines: leak and rupture. All the minimal cut sets (MCS) are achieved by Fussel calculation. They are consisted of 25 first order MCSs, 6 third MCSs and 21 fourth MCSs; The basic factors resulting pipelines in failure are investigated through the qualitative and quantitative analyses. By analyzing the fault tree of pipelines and its minimal cut sets, it is found that external interference from the third party, corrosion, incorrect operation and material defects are the major reasons to cause the failure of pipelines. And this paper gives some relevant measurements to improve the pipelines. The results of fault tree analysis show that this method can provide some theoretical guides for the maintenance of old pipelines and design of new pipelines.