Abstract: Compared with the individual combustion process, the mixed combustion of methane and hydrogen has the advantages of reducing carbon emissions and improving energy flexibility. A molecular simulation method was used to study the co-combustion characteristics of methane and hydrogen in reaction systems of air and oxygen-enriched atmospheres. The results show that the consumption rate of CH₄ under a high volume fraction of CO₂ is smaller than that in an air atmosphere, because CO₂ is chemically inert at low temperatures. Whereas under high-temperature conditions, the rapid oxidizing property of CO₂ accelerates the consumption of methane and hydrogen. In both air and oxygen-enriched atmospheres, when the hydrogen blending ratio is 0.5, hydrogen promotes the combustion of methane. The elevation of ambient pressure can accelerate the combustion of methane and hydrogen, but under oxygen-enriched conditions, the CH₄ consumption rate is lower than in the air atmosphere, with the main reason being that the increase in pressure strengthens the intermolecular forces of CO₂, causing it to exhibit chemical inertness. With the increase of O₂ volume fraction, the combustion rates of CH₄ and H₂ increase in both atmospheres, but the consumption rate of CH₄ in the air atmosphere is greater than that in the oxygen-enriched atmosphere. Temperature, hydrogen blending ratio, pressure, and equivalence ratio have a relatively small effect on the overall reaction pathway of methane-hydrogen blended combustion, but the reaction atmosphere affects the gas combustion rate by influencing the initial reaction time of certain key reactions.