A modified DDLC-MH(81) equation of state was proposed to correlate binary vapor - liquid equilibrum data in literature for a propane - ethanol - water system. The binary interaction parameters were linear functions of temperatures. The vapor - liquid equilibrium data for the binary and ternary systems were determined by means of a circulation apparatus. The experimental results were in good agreement with predicted results by using the model. Then the phase behavior of the ternary system under supercritical propane condition was predicted. The results showed that the solubilities and selectivities of ethanol solutions by using super - critical propane as solvent were better than supercritical carbon dioxide under the condition that the ethanol mole fractions in liquid phase were more than 0. 2.