Abstract: The most of in-service oil and/or gas transmission pipelines at present in China are aged pipelines, the accident rates are going high.The assessment technology of pipeline integrity should be urgently developed because it is very helpful to ensure satefy and reliability of pipeline operation.From the point of quantitative analysis of pipeline safety onward, the authors introduce the research status quo of pipeline integrity, and put forward the conception of "in-service pipeline integrity" and its substance as well as objective in the light of in-service pipelines in China, briefly describe the future research key-point and development tendency on the assessment technology of pipeline integrity at home and abroad.