Abstract: In order to adapt to the large-scale networking development status of domestic gas pipeline industry, the gas transmission assurance capacity of the whole pipeline network system in the operation period is widely concerned, and it is particularly important to evaluate its reliability to accomplish the task of gas transmission. In this paper, pipeline network system reliability index, system reliability calculation, unit reliability calculation, reliability data and reliability management were studied focusing on the safety, efficient operation and management of large-scale gas pipeline network system. A three-layer system reliability evaluation index system was developed, including reliability, maintenance and robustness. Then, a distributed step calculation model of physical pipeline network system reliability based on pipeline process simulation technology was established to calculate the reliability of pipeline network/pipeline/station system simply and quickly. Finally, this calculation model was applied to one certain gas compressor station for case calculation. The topological structure of the pipeline network was split into reliability frameworks of different levels from the top to the bottom in the sequence of station system→typical structure→basic loop→equipment unit. Afterwards, the reliability of each level was calculated from the bottom to the top by using the reliability of individual equipment. Thus, the reliability of the gas compressor station in different compressor stop/start schemes was obtained. The research results provide the foundation for the reliability evaluation and management of large-scale gas pipeline network systems in the future.