Abstract: Aiming at the adsorption capacity of coal molecules to gas and the difference of competitive adsorption, taking Heilongguan bituminous coal molecule as the research object, the adsorption behavior of gas under different conditions was simulated by using the grand canonical ensemble Monte Carlo method. The adsorption competitiveness of coal to gas was analyzed from the molecular scale, and the micro process of coal molecule adsorption was discussed. The results show that the adsorption constants a and b are negative correlation to temperature. As the temperature increases, the gas adsorption amount decreases, indicating that high temperature is not conducive to gas adsorption. Compared with CH₄ and N₂, coal molecules have stronger van der Waals energy and electrostatic energy when they adsorb CO₂. The energy released by adsorbing single-component CO₂ is more than that released by adsorbing two-component mixed gas. The more total energy released, the easier adsorption is to occur. In the energy distribution, compared with the single-component CO₂, the adsorption potential energy peak of CO₂ in the two-component mixed system moves to the region with weak interaction, indicating that the addition of CH₄ and N₂ will affect the adsorption capacity of CO₂, and the effect of CH₄ on the adsorption of CO₂ is greater than that of N₂. In the mixed adsorption of CH₄ and N₂, CH₄ is in the dominant position.