Abstract: The long distance oil/gas pipelines are usually buried pipelines. The failure has gone with it since the pipelines used. The major factors are stress.corrosion, external interference and so on. Rapture and perforation are the main failure types of crude oil pipeline. And the failure will shorten the reliability and service life of the oil/gas pipelines. Based on the analysis of failure factors, the fault tree of crude oil/gas pipelines is put forward, and each order minimum cut sets, weakness and fault probability are obtained. In the paper, some measures of improving reliability of long distance oil/gas pipelines are presented.