In order to identify the vulnerable links in urban natural gas pipeline network systems, this study established a concept for the vulnerability analysis of the network system, providing a basis for quantitative analysis of vulnerability. The criteria for selecting nodes in the network were determined based on the network composition. Based on the theory of disaster chain, the vulnerability factors were analyzed thoroughly, the hazard factors causing vulnerability were determined and the vulnerable parts of the network system were identified. A model for the calculation of the structural threats from the network itself was established. The first step is to identify the interdicted point of single pipeline sections through the calculation method for friction resistance loss, and the second step is to determine the key nodes with the maximum or minimum vulnerability of the entire network, thereby realizing the point-to-net analysis of the pipeline network. The FIM model was implemented, combining the geological information system ArcGIS, Java programming language, and Lingo optimization software. Using a natural gas pipeline network in Beijing as a case study, the distribution of vulnerable points in the network was plotted and the key nodes with high vulnerability were identified by analyses of vulnerability and importance.