Abstract <p>A generalized two-step model of chemical kinetics for the detonation combustion of a stoichiometric binary mixture of methane with hydrogen and air is proposed. It can be used to calculate the heat release of the chemical reaction and the molar mass, internal energy, and adiabatic index of the mixture without calculating its detailed chemical composition, which greatly simplifies kinetic calculations and reduces their amount compared to detailed kinetics. The model is physically based and contains no fitting parameters. A numerical two-dimensional calculation of the multifront structure of the detonation wave is performed for the mixture with varying fuel ratio. Chemical transformations are described using the proposed kinetic model. The calculated detonation cell size and the qualitative structure of the detonation wave (the presence of regions of unburned gas in the reaction zone and the irregularity of the cellular structure due to the formation of both primary and secondary transverse waves) agree well with experiment.</p>