Abstract: Thermodynamic parameters are important parameters to describe the state of substance in the adsorption process. The methane adsorption isotherms of coal samples with different metamorphic degrees were measured using a high-pressure isothermal adsorption instrument. Combined with the standard Gibbs free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°), to study the methane adsorption state on the coal surface under different temperature conditions. The results show that the methane adsorption on the coal surface is a exothermic and reversible physical process. Under the low-temperature condition, the methane adsorption capacity decreases obviously due to the temperature increase, and the adsorption capacity decreases slowly after the temperature exceeds 40°C. The adsorption process is mostly thermodynamically spontaneous. Under the high temperature and pressure conditions, the gas in the coal surface is more likely to desorb into a free gas state.