Abstract: To determine a suitable development mode and enhance condensate oil recovery in high-CO2 condensate gas reservoir,the phase changing behavior of condensate gas flow in the development process was identified.The HTHP Multi-functional Fluid Analyzer was used in single flash vaporization test,dew point pressure test,constant component expansion test,and constant volume depletion test for high-CO2 condensate gas samples with different mole fractions,and the impacts of such fractions on the phase behavior and HP physical parameters were also compared.With higher mole fraction of CO2,the rate of retrograde condensation dropped,the peak of retrograde condensation liquid decreased by about 15%,the recovery factor of condensate oil increased by about 20%,the recovery of natural gas was about 85%,and the phase envelope curve shrank inwards.CO2 in the system contributes to higher condensate recovery by inhibiting its retrograde condensation and enhancing the retrograde vaporization.It is significant for determining a reasonable production strategy.