In this study, a methodology to evaluate gas supply reliability of the natural gas pipeline network is proposed, and the uncertainty of the gas supply capacity of the natural gas resources is considered. The methodology is composed of four parts. Firstly, the gas supply capacity calculation model of natural gas resources considering its stochastic and time-dependent characteristics is described. Secondly, the gas demand prediction model is developed based on the demand-side analysis. Thirdly, the gas supply calculation model of natural gas pipeline network is proposed considering units failure and hydraulic characteristics. Finally, according to the established gas supply reliability index system, the gas supply reliability indicators are calculated based on N (N is a large number) times of Monte Carlo simulation. Furthermore, a real natural gas pipeline network located in China is applied to confirm the feasibility of the methodology, and the gas supply reliability is evaluated based on quantity and time dimensions, and the results are reduced by about 3.9% and 4.1% compared with the results calculated by the method which ignored the uncertainty of resources. At last, the significance of the natural gas resources in the gas supply reliability is investigated by the sensitivity analysis.