Abstract: In order to accurately measure the coal gas adsorption capacity and gas content under the influence of water content, soft and hard anthracite is taken as the research object, and molecular adsorption module is used to establish the coal macromolecular structure model of four coal samples under the conditions of 0%, 1%, 3% and 5% water content. The applicability of linear equation, traditional linear equation, power function equation and exponential equation in quantitative characterization of water content was further compared. The results show that the isothermal adsorption curves of soft and hard coals under different moisture content conform to the characteristics of type I isotherm, and the Langmuir volume of soft coal is higher than that of hard coal, and the Langmuir volume of the four anthracite coals is most sensitive to the change of water content when the moisture content is 0%-1%. The water influence coefficient of soft and hard anthracite gas adsorption capacity under water effect is more suitable for linear equation characterization. At the same time, the influence degree coefficient a of water content of soft coal is small, that is, the change of water content has a more significant influence on the gas adsorption capacity of soft coal.