High pressure sorption isotherms of pure CH4and CO2at 80 °C and CH4/CO2mixtures at 30 and 80 °C on shale samples from Sichuan Basin, China, were measured by a modified volumetric method. The multicomponent sorption measurements were conducted on the mixtures with feed gas compositions of 79.50% and 48.62% CH4. The sorption isotherms of pure CH4and CO2were fitted by a modified Langmuir equation, and the sorption isotherms of the total and individual component of CH4/CO2mixtures were fitted by an extended Langmuir (EL) equation. Qualitative and quantitative characterizations of selective sorption of CH4and CO2were discussed at different temperatures and gas compositions. The results indicate that the sorption capacity of pure CO2is larger than that of pure CH4, with the Langmuir sorption capacity of pure CO2being approximately 2.5 times of pure CH4. However, a higher sorption amount of CH4than CO2is obtained in competitive sorption of mixed gas with a feed gas composition of 79.50% CH4, suggesting that sorption behavior of individual component under competitive condition depends not only on the sorption affinity of the component, but also on the partial pressure of the component in the mixture. The separation factors calculated from multicomponent sorption data are in a range of 1.0–2.5, which are far less than that calculated from single gas sorption data, indicating that the presence of CH4greatly weakens the preferential sorption of CO2. On the contrary, increasing temperature and CO2content in the mixture will promote preferential sorption of CO2.