Abstract: The electrochemical behaviors of N80 steel and 09Cr2AlMoRE steel in stratum water with saturated CO2 were comparably investigated using electrochemical impedance spectra (EIS),and the microstructures of corrosion scales formed on two samples at 1 MPa,120 ℃ for 7 days were also observed by SEM. The results showed that the anodic impedance of N80 steel was consisted of capacitance at high frequency,inductance at middle frequency and capacitance at low frequency. While for the anodic impedance of novel alloy,the spectra was only consisted of capacitance at high and low frequencies,and the inductance shrinked. For the cathodic impedance spectras of two samples,the spectra of N80 steel was only consisted of one capacitance,and the spectra of novel alloy were consisted of capacitance at high frequency,Warburg impedance at middle frequency and capacitance at low frequency. Calculating the polarization impedances of anodic and cathodic processes for two samples,it revealed that the polarization impedances of anodic and cathodic processes for novel alloy were all higher than that for N80 steel,this means that the novel alloy can effectively inhibited the occurrence of CO2 corrosion formed on it.