Two-phase equilibrium data was measured for carbon dioxide and monoolein system by using a phase equilibrium loading re-circulation high-pressure type apparatus at various pressures and at temperatures of 60, 80 and 100 ºC. The experimental data was compared with the data calculated from the regular solution equations. It concluded that the assessment of the feasibility of the extraction process utilizing a near critical solvent would be speeded up if it was possible to predict the solubility data. A thermodynamic procedure is employed to each phase by applying activity coefficient expressions based on the regular solution theory. It was also found that the interaction parameters which were necessary parameters in activity coefficients calculation were pressure dependent.