Abstract: The propagation law of shock wave and the dynamic responses of steel a frame structure subjected to internal gas explosion are investigated, and some blast-resistant design suggestions of steel a frame structure are presented. Finit element models of a steel frame structure, explosive gas and air are established using ANSYS/LS-DYNA dynamic analysis software, and the dynamic responses of a three-story steel frame structure subjected to internal gas explosion are analyzed based on a fluid-structure coupling method. The gas explosion propagation process and the characteristics of the shock wave overpressure on the different structural positions are studied. The deformation characteristics of beams and columns under different methane concentrations are analyzed and compared. The results show that the fluid-structure coupling method can well simulate shock wave propagation process of internal gas explosion. The structural effect is greater when explosive gas initial energy is higher. The structural deformation has locality and weak transitivity under blast loading. A steel frame structure is a good blast-resistant structural system when explosive gas initial energy is smaller, and after the wall and floor are destroyed, beams and columns do not damage and even cause progressive collapse of the structure.