The passivity of 13Cr stainless steel in 1% NaCl solution under dynamic supercritical CO2 (SC-CO2) conditions without or with different partial pressures of O-2 was studied by electrochemical measurements and surface characterization. Electrochemical measurements indicate that both the fluid flow and an increase in CO2 pressure lead to a decrease m the stability of the passive film. Introduction of 0.1 MPa O-2 into the dynamic SC-CO2 system facilitates the formation of a stable and integrated passive film, which enhances the corrosion resistance of 13Cr stainless steel. However, the addition of 1 MPa O-2 reduces the stability of the passive film and results in the formation of a passive film with high donor density, which decreases the corrosion resistance of 13Cr stainless steel.