Abstract: Complex and extraordinary random, and very difficult to forecast and control is one of the major factors for oil and gas pipeline's third party damage.In allusion to the third party damage factors, the third party damage fault tree is established, qualitative and quantitative analysis is carried out for the invalidation of oil and gas pipeline's third party damage by fault tree analysis method.Minimum cut set is received and the major factor of third party damage that caused pipeline disabled is identified.Probability of top event is educed through minimum cut set, which form a method to analyze the important degree of elementary event and quantitative analysis-based mode.The authors consider that the analysis method based on the third party damage fault tree of the oil and pipeline can provide an reference for pipeline route selection and safety design.