Monte Carlo method was applied to calculate the solubilities of naphthalene, phenanthrene, and anthracene in supercritical carbon dioxide, ethane, and ethylene. Supercritical fluids were treated as single-site molecules and aromatic compounds were treated as two-site (two benzene groups) or three-site (three benzene groups) molecules, The Lennard-Jones potential was used as the site-site potential. A modified test particle method was used to calculate the residual chemical potential of aromatic compounds in supercritical fluids based on the NVT canonical ensemble. The calculated results of solubilities show good agreement with the experimental values. Moreover, the solubilities of isomers can be distinguished by the present site model and common potential parameters. The microscopic structures of supercritical carbon dioxide around phenanthrene and anthracene are found to be different by calculation of the radial distribution functions.