Based on the results of isothermal adsorption experiments on 184 middlerank coal samples under equilibrium moistures (with vitrinite reflectances of between 0.65% and 2.50%), this study simulates the relationship between Langmuir volume and Langmuir pressure in the middlerank coal; establishes the master curve of saturated adsorption methane content of different coal rank under various buried depths (temperature and pressure); discusses the integrated effect of middlerank coal adsorption and the difference of isothermal adsorption characteristics between middlerank and low, high rank coals. In the end, this study proposes a prediction method for adsorption methane content of middlerank coal.