The identification of key links in a comprehensive energy system is of great significance for the research and improvement of system vulnerability. Aiming at the problem that the traditional reductionism method can not explain the system level and the influence of energy flow is not considered in the analysis of complex network, a key link identification method of the IES based on power flow and complex network structure is proposed. Firstly, a comprehensive energy complex network model is established based on power flow, and the mathematical model parameters and power flow results of the IES are introduced into the modeling of complex network to make the model more suitable for realistic operating conditions. Secondly, based on the power flow calculation results and complex network parameters, two evaluation indicators, i.e. node energy degree and energy edge intermediate, are proposed to improve the identification accuracy of key links. Finally, based on the established model, the key links are destroyed and the changes in network efficiency are observed. Compared with other attack modes, the feasibility of the proposed method is verified.