Abstract: Within the framework of integrated energy system（IES）, the energy interaction among the energy subsystems is increasing. The cooperation of multi-energy system not only improves the operation economy, but also makes it difficult to apply the traditional security analysis method of single energy subsystem to the IES. It is necessary to conduct an in-depth analysis of the static security problem of the electric-gas-heat IES. Firstly, a mathematical model of IES is established including electricity, gas and heat, and the static multi-energy flow of the IES is calculated. Secondly, two control modes are proposed for the IES coupling components, i.e. mutual control mode and protection control mode. On this basis, the predicted accident set is established, and the static N-1 security check is performed on the IES. By analyzing the static N-1 security check result of the IES, the impact of the exit of the coupling element and the different control modes of the coupling element on the operational security of IES is studied. Finally, the accuracy and effectiveness of the proposed static N-1 security analysis method of the IES are analyzed and verified by the IES 14-node test system.