Abstract: The immersion corrosion test and electrochemical test for microbial corrosion resistant steel were carried out in the coexistence environment of sulfate-reducing bacteria (SRB) and CO₂. The corrosion morphology and composition of corrosion products were observed and analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results show that in the coexistence environment of SRB and CO₂, SRB could inhibit the corrosion of CO₂, and with the increase of SRB content, the uniform corrosion rate decreased, but SRB improved the occurrence and development of pitting corrosion. When the SRB content was high enough, a dense and protective FeS film formed on the surface of the sample, making the corrosion rate and pit size decrease obviously. With the increase of SRB content, the radius of impedance arc increased, and the corrosion resistance of microbial corrosion resistant steel improved. When the SRB inoculum size was 0.2%, the anodic reaction was dominated by activated dissolution, and the corrosion rate was controlled by the cathodic reaction. When the SRB inoculum size was increased to 2% and 20%, the anodic reaction was inhibited by the dense FeS corrosion product film, so the corrosion rate was controlled by the anodic reaction.