Abstract: With the rapid development of the integrated energy system,the electricity-gas coupling interconnection system has become a typical form of the energy Internet system.In order to ensure the safe and efficient operation of the electricity-gas interconnected network and improve the monitoring status awareness and bad data defense capabilities of the smart energy system,this paper refers to the grid state estimation method and separately analyzes the power grid and the gas grid. Using voltage modulus and phase angle of grid nodes and pressure square of gas network nodes as state quantities,based on the maximum exponential square（MES）method,and considering zero injection constraint and boundary equality constraint of the grid and gas network,the MES state estimation model of electricity-gas coupling network is established and the global unified coordination state of the electricity-gas coupling network is estimated. The simulation is based on a 4 grid node-12 gas grid node coupling system. The simulation results prove that the method proposed in this paper can realize the accurate perception of the operation status of the electricity-gas coupling network,and on this basis,the global consistent solution of the electricity-gas coupling network is obtained. At the same time,the coupling relationship can also be used at the coupling boundary of the two to realize effective identification of bad data on the boundary.