On purpose of studying volume expansion of CO2 + oil system at near critical and supercritical conditions of CO2, a pressure-volume-temperature (PVT) cell with visible window was used for measuring the liquid volume of CO2 + kerosene, tetradecane, white oil and mixing oil, and the solubility of CO2 in the oils at 313.15 K with different pressures. The results of the study showed that the dispersion state of CO2 molecules in oil phase under near critical or supercritical condition of CO2 play a dominate role for increasing the volume of CO2 + oil systems, especially for light fraction oil, and as pressure being increased, the solubility of CO2 in oil increases which cause increasing of the distance between oil molecules and decreasing of intermolecular force operating within oil molecule, consequently caused the oil volume expansion. (C) 2013 Elsevier Ltd. All rights reserved.