The phase behaviors of three microemulsion systems were studied in a custom-made volume-variable view cell, including the ternary system of CO2/EtOH (ethanol)/1,3-PDO (1,3-propanediol), quaternary system of CO2/EtOH/H2O/1,3-PDO and quinary system of AOT/CO2/EtOH/H2O/1,3-PDO, using 1,3-PDO as the model compound, AOT (sodium bis(2-ethylhexyl) sulfosuccinate) as surfactant and ethanol as co-solvent in the CO2 continuous phase. The phase behaviors of the AOT/CO2/EtOH/H2O/1,3-PDO quinary system were mainly discussed in the temperature range of 29.1 degrees C-44.3 degrees C and pressure range of 6.41MPa-15.95MPa. The result shows that a thermodynamically stable microemulsion can be formed by controlling the operating pressures and temperatures, which can provide basic thermodynamics data for industrial design and proper operating conditions for selectively solubilizing 1,3-PDO from dilute aqueous solution.