Abstract: Gas trunk line is an important strategic energy channel in China. Its reliability evaluation is pivotal for achieving the social and economic benefits of the pipeline. However, this field of research has not yet started in China. In this paper, the reliability of gas trunk line is discussed from two aspects: evaluation index and calculation model. A dynamic analysis model based on "gas source-pipeline system-peak shaving-user" process and considering the gas supply reliability is established, which can be used to evaluate the reliability of gas trunk line by the combination of hydraulic and thermal simulation and statistics. Moreover, specific suggestions and guidance are put forward to the reliability evaluation of the gas supply system in the future.