The activated mesocarbon microbeads (a-MCMBs) with high BET specific surface area of 3180m(2)/g are prepared. Experimental characterization of a-MCMBs is carried out in terms of the adsorption isotherm of nitrogen at 77 K by the ASAP-2010 apparatus. Then, methane and hydrogen adsorption isotherms on a-MCMBs are measured by the IGA-003 gravimetric analyzer at 298 K and 77 K. The pores of a-MCMBs are described as slit-shaped with a pore size distribution (PSD). The PSD is determined by a combined method of grand canonical Monte Carlo (GCMC) simulation and statistics integral equation (SIE) from the experimental isotherm of nitrogen on a-MCMBs. In GCMC simulation, methane and hydrogen molecules are modeled as the Lennard-Jones spherical molecules, and the well-known Steele's 10-4-3 potential is used to represent the interaction between the fluid molecule and the solid wall. Good agreement between simulated and experimental data indicates that our model represents well the mechanism of adsorption on a-MCMBs. Then, this model is used to predict adsorption of methane and hydrogen over a wide range of pressure up to 12 MPa. The prediction shows that adsorption amount of methane reaches 36 wt % at 298 K and 4 MPa, which is superior to the results in the literature. The hydrogen adsorption amount at 10 MPa can reach 3.2 wt % and 15 wt % at 298 K and 77 K, respectively, which are also higher scores, compared with the other carbon materials.