Molecular dynamics simulation has been used to evaluate the reliability of high-pressure diffusion coefficients of binary mixtures.Diffusion coefficients of high boiling compounds in supercritical fluids are important for the design of supercritical extractors,separators and reactors [1-2].Since high-pressure experiments are time intensive and difficult to perform,molecular simulation could prove a useful tool to obtain thermodynamic properties,however the reliability is still in question.In this work,an NVT ensemble single site model molecular dynamics simulation using gear predictor corrector algorithm has been applied to calculate diffusion coefficients of carbon dioxide,naphthalene,2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene in supercritical carbon dioxide system at 317.5K [3].The Lennard-Jones (12-6) and the Coulomb potential function have been combined to an intermolecular potential function to measure the interaction between a pair of molecules.The simulation results of the diffusion coefficients are compared with the experimental data [4] near the critical points.As shown in figure 1,the calculated diffusion coefficients for each system behaved as a monotonic decreasing function of the molar density.In this study the molecular simulations data and the selected experimental data showed good agreement even near the critical point of carbon dioxide.