Ab initio quantum chemical calculations were done for a system of a benzene molecule and a carbon dioxide molecule for a lot of relative configurations. Since intermolecular interactions in this system were considered to be small at some configurations, the calculations were carried out with 6-31G* basis set and the 2nd order Moller-Plesset perturbation method. The resultant potential surface was explained in detail using four representative configurations. At the short intermolecular distance, the interaction showed strong dependence on the relative configurations. On the basis of these data, an analytical pair potential function was proposed for the benzene-CO2 system. Using this potential model, we have done Monte Carlo calculations for the CO2 fluid containing one benzene molecule at several supercritical conditions. Our model was confirmed to reflect the shape of a plate-like molecule on the solvent structures.