Thermochemical energy storage is an important energy storage technology, which has become a focus of technology in recent years. The methane steam reforming reaction is a thermochemical energy storage reaction, and it is the main method for industrial hydrogen production. The methane steam reforming reaction is a strongly endothermic reaction. In the present study, the simulation of the methane steam reforming reaction in the reactors is commonly calculated. There are two main methods of simulation: macro-scale simulation and pore-scale simulation. Equivalent media model of macro-scale simulation is adopted. This method has advantages of less calculation time and highly accurate results. The structure of the packed bed has an important influence on the reaction performance. The grille-sphere composite packed bed has good reaction performance. The axially varying particle size in a single channel of the grid has the effect of improving the reaction performance. In this article, the equivalent medium model simulation was used to verify the performance advantage of the axially-varying particle in the whole grid- particle composite packing bed. This work has great significance in guiding industrial production.