Abstract: Shale gas isothermal adsorption experiments are mostly experiments above the critical temperature, the adsorption quantity obtained from the experiments is excess adsorption. In order to study super-critical isothermal adsorption mechanism of the shale gas, the weighting method was used in this study, the high pressure isothermal adsorption experiment have been made for methane and carbon dioxide in shale above the critical temperature. Based on the analysis of the typical adsorption and super-critical adsorption difference, through modified super-critical isothermal adsorption model (Langmuir equation and pore filling (Dubinin Radushkevich D-R)), experimental data were fitted. Study indicates that the simple Langmuir equation can approximately fit experimental data of methane adsorption, but the accuracy is not high, and can't fit carbon adsorption data. When the density of the adsorbed phase as parameter can be optimized, the modified microporous packing model and the Langmuir model can fit well adsorption data of methane and carbon dioxide, Fitting effect is the best with the modified microporous packing model, the adsorption phase density of super-critical methane is consistent with literature reports, suggesting that adsorbed gas may exists in the form of pore filling.