In order to investigate the characteristics of methane adsorption by raw coal at high temperatures related to a project of coalbed methane exploitation using heat injection, thermostability adsorption apparatus and auxiliary sealing materials were manufactured and a series of experiments were carried out to investigate the monomolecular layer adsorption of methane on coal at 30-270 degrees C temperatures and 0.1-7.0 MPa gas pressures. Constant-volume experiments indicated decreasing adsorption capacity rates at higher temperatures; constant gas pressure cases showed the opposite effect. The values of the parameters in the Langmuir isotherm equation were seen to decrease exponentially with increasing temperature.