Abstract: The research on supercritical methane isothermal adsorption model in shale is of great significance for shale gas reserve assessment, production dynamics prediction and development program preparation. Based on the supercritical methane isothermal adsorption theory and molecular dynamics simulation results, the DA-BET supercritical methane isothermal adsorption model was established considering the differences of adsorption mechanisms in different scale spaces, characterizing the methane molecule adsorption in micropores and mesopores/macropores by use of DA micropore filling model and BET multimolecular layer adsorption model, repectively. On this basis, the model fitting method and fitting effect were analyzed using high temperature and high pressure experimental data, and the contribution of different adsorption mechanisms to supercritical methane isothermal adsorption in shale was also explored. The results show that the DA-BET supercritical methane isothermal adsorption model can highly accurately fit the experimental data, and the adsorption characteristic curves obtained by calculationsatisfy the uniqueness, and the model can be used to predict the methane adsorption capacity of shale at high temperature. In the low-pressure stage, methane molecules are predominantly adsorbed by micropore filling; temperature and pressure significantly affect the contribution of different adsorption mechanisms to the total adsorption; the lower the temperature and the higher the pressure, the smaller the contribution of micropore filling adsorption to the total adsorption capacity.