In this paper, activated carbon models with different pore size distribution (PSD) and oxidation degree were constructed, and the adsorption processes of benzene on models under 303.15 K were analyzed by molecular simulation technology. The adsorption mechanisms including adsorption isotherms, energy changes, PSD changes after benzene adsorption, radial distribution functions (RDFs), and diffusion coefficients were discussed in detail. This can provide guidance for micro-control of activated carbon structure and more reasonable selection in practical applications.