<p>Storage of multiphase and multicomponent fluids in coal is crucial for accurate reserve estimation and effective exploration. A macromolecular model of anthracite was built, and adsorptions of pure gas and gas mixture of CO₂ and CH₄ under a series of low temperatures (233.15–313.15 °K), pressures (0–30&#xa0;MPa) and water content (0–2.74%) conditions were simulated. The absolute adsorption of each component increased with pressure and its molar fraction decreased with increase in temperature and water content. CO₂ had a larger adsorption capacity, isosteric heat and interaction energies compared with CH₄ due to its smaller size and quadrupole moment. The interaction energy was positively related to the adsorption amount. The adsorption selectivity of CO₂ over CH₄ decreased with increase in CO₂ partial pressure and temperature, while it increased with water content due to a significant reduction in the accessible volume for CH₄. The adsorbate distribution peaks on the N- and O-functional groups reduced while those on the S-functional group increased with increase in water content. The density of CH₄ decreased significantly with increase in CO₂ molar fraction, and its distribution area was smaller than that of CO₂.</p>