Abstract: The reliability of natural gas pipeline network system is affected by many factors, so the reliability calculation method under ultimate limit state cannot satisfy actual demand. Random variables of various types can be used to calculate the probability of natural gas pipeline network system reliability under multi-state conditions and reveal the variation of pipeline network operation parameters. The pipeline operation parameters are converted into standard independent random variables so as to simplify the probability calculation process for pipeline network reliability by marginal distribution functions. With comprehensive assessment of the supply capacity of natural gas pipeline network and economic benefit of both buyer and seller in natural gas market, the supply reliability of pipeline is combined with financial risk ratios of market transactions to establish calculation methods of both buyer and seller's satisfaction. This newly developed technique may provide natural gas pipeline operation and market decision with quantitative analysis tools.