Abstract: In order to improve the understanding of pipeline accidents, predict and prevent pipeline accidents better, the accident characteristics were summarized and sorted, and the essential characteristics of the accidents were clearly described. A new evaluation and description model was proposed to quantitatively describe the states of pipeline accidents by the indicators of fragility, anti-fragility and integrity. The fragility of pipeline system is the occurring tendency of potential accidents when the internal and external factors change, which is used to describe the possibility of known defects or intact states evolving into accidents. The anti-fragility describes that the emergency measures and integrity management get better after the change of internal and external factors or even accident happens. It means that pipeline system is getting better in preventing accidents. The integrity of pipeline system represents that pipelines are physically in good conditions with stronger capacity to resist the change of various factors. This new model differs from the traditional risk assessment, which has a clearer understanding and assessment of the nature of the accident, and will have a certain guiding role in the improvement of risk assessment techniques.