Abstract: Based on the fluid-structure coupling method, the gas explosion shock wave characteristics and actions on the structures subjected to internal gas explosion are analyzed, using ANSYS/LS-DYNA dynamic analysis software. Finite element models are established using ANSYS. The Euler grids and multiple material ALE algorithms are adopted for flammable mixture gas and air. The influencing factors of the explosion shock wave the volume ratios of flammable gas to air, the volume and explosion pressure-release parts are analyzed. Nine kinds of working conditions for numerical analysis are selected. The analysis results show that the explosion shock wave pressure is the maximum when the volume ratio of flammable gas to air reaches 9.5%. The explosion shock wave propagation law and structural effect process under an internal gas explosion can well be simulated by the fluid-structure coupling method. The destructive effect of a structure can be reduced with setting up reasonable relief pressure openings when a flammable gas explosion happen in a closed space.