The effect of biocide and D-amino acid on the corrosion behavior of 20# carbon steel, N80 steel and P110 steel in the media of SRB+IOB mixed bacteria, was comparatively assessed by using weight loss method, electrochemical measurements and SEM. In the tests without biocide, P110 suffered from severe corrosion with weight loss of 0.278 mm/a, while weight loss of 20# and N80 were 0.149 and 0.148 mm/a respectively, while uniform and dense biofilms with deposited corrosion products formed on the surface of all the steels; in the tests with biocide, the corrosion of the three steels slowed down, it is found that the formed rust scales on the surface of steels with significantly lower content of Ca Mg, P, and S, but with cracks and spallation steels. The electrochemical measurement results also revealed that the corrosion rate of three steels was significantly reduced when they were immersed for 14 d in the corrosive media with addition of biocides. The corrosion mechanism of SRB and IOB mixed bacteria is probably due to that SRB oxidizes Fe to Fe²⁺ through its own metabolism, and Fe²⁺ is further oxidized by IOB to Fe³⁺, and IOB provides environmental conditions for SRB so as to form a synergistic effect. It is proposed that D-amino acids and biocide effectively inhibit MIC behavior by regulating the bacterial gene expression and destroys the cell structure, as well as the oxygen concentration difference environment. Due to the different content of C, Cu and others, the corrosion rate of the three steels may be different under the sterile conditions.