Abstract: The adsorption of coal to CH₄, CO₂ and its multi-component gas is one of the basic parameters of CO₂-ECBM technology, and it is also the basis for evaluating CO₂ storage and CH4 gas production. Aiming at the cumbersome and time-consuming experiment of coal adsorption mixed gas, the adsorption isotherms of CO₂, CH₄ and their mixed gases were measured by isothermal adsorption experiment and the adsorption coefficients of mixed gases a, b and CO₂ volume fraction were proposed. By fitting the equation, the prediction method of CO₂ and CH₄ mixed gas adsorption amount is obtained. The main conclusions are as follows: the equilibrium time of CO₂ adsorption by C₁₃ coal in Huainan Mining Area is about 24 h, which is much higher than the adsorption equilibrium time of CH₄; the adsorption capacity of C₁₃ coal for CO₂ is more than twice that of CH₄. The adsorption amount of C13 coal to the mixed gas increases with the increase of CO₂ volume fraction; the adsorption constant a, b values and carbon dioxide volume fraction are in quadratic function relationship. According to the fitting equation, the Langmuir equation can be used to calculate the adsorption capacity of CO₂ and CH₄ mixed gas in any volume ratio.