Abstract: In order to accurately definite identify the weakness of gas pipeline network system accurately, the vulnerability analysis theory thereof is established with starting from the concept of vulnerability, vulnerability analysis theory of gas pipeline system is established and combining with the characteristics of the pipeline system. Based on disaster chain theory, vulnerability factors elements of the system is analyzed deeply, and external destructive threats inducing the vulnerability and the vulnerable parts of the system are identified. Vulnerability calculating model of external threats is established. Using the historical data, together with expert consultation, severity and functional unavailability of external natural threats are analyzed qualitatively. With the Markov potential impact model, severity of human threats is quantified. Moreover, the hydraulic calculation software of gas pipeline network is used to define the functional unavailability of human threats. Taking the regional high pressure gas pipeline network in Beijing as an example, vulnerability analysis is conducted, and its key parts with high vulnerability are determined.