Abstract: Different coal samples were tested for their adsorptive capacities so as to determine their adsorbability parameters with CO2, CH4 and N2 as adsorbates. According to moistened length as adsorbed by porous media, model of pore structure, surface physico-chemistry and elasticity, the formulas of adsorptive expansion stress and strain of coal mass are derived. In addition, the influence of such parameters as adsorption constants, temperature, gas pressure, specific surface area of coal mass and the cross section area adsorbing gas molecules on the stress and strain are discussed. The formulas can be used more widely than existing ones and easy to calculate the strain and stress under different restrictive conditions. The bigger the specific surface area of coal mass and the cross-section area adsorbing gas molecules, the higher the gas adsorbability and the adsorptive expansion stress and strain of coal mass.