Grand canonical Monte Carlo (GCMC) simulations were carried out to investigate the adsorption of CH4 and CO2 mixture on an ordered carbon material CMK-1. In the simulation, the fluid molecules are both modeled as Lennard-Jones spheres, and the CMK-1 adsorbent is characterized by the rod-aligned slitlike (RSP) pore model to emphasize its textural and grooved structure. The effects of temperature, pressure, pore width, and bulk composition on adsorption have been conducted in details. Adsorption amounts, local density profiles, snapshots and the solid-fluid potential curves are also extensively analyzed to provide deep insight into the separation mechanism. We finally investigate the adsorption behavior in the real CMK-1, with a pore size distribution (PSD) to characterize the heterogeneity of adsorbent. The optimum operating condition is obtained at T = 308 K, P = 7.0 MPa and the bulk composition y(CO2) = 0.2. corresponding to the greatest selectivity of 3.55. Our results show that CMK-1 might be a promising adsorbent for the separation of a rich CH4 natural gas. (C) 2009 Elsevier B.V. All rights reserved.