The electrochemical corrosion behavior of X70 steel in NaCl solution under aerobic anaerobic and CO2 conditions at 90 C were investigated. Liner polarization resistance (LPR) electrochemical impedance spectroscopy (EIS) technologies were used to study the electrochemical characteristics of X70 with different conditions SEM EDS and XRD were used to investigate the scale characterization. The results showed that the corrosion rate under aerobic condition were much higher than that under anaerobic condition. EIS measured under aerobic and anaerobic conditions with different immersion time all consisted of a high frequency capacitive semicircle and a low frequency capacitive semicircle. Under aerobic condition the diameter of capacitive semicircle increased firstly then decreased after 36 h immersion which indicated the corrosion scale formed had limited protectiveness while the diameter of capacitive semicircle measured at anaerobic condition increased with increasing immersion time which indicated the corrosion scale formed at this condition had better protectiveness.