Objective To study the corrosion characteristics and determine the corrosion mechanism of 2507 duplex stainless steel in circulating cooling water simulated solution containing SRB+IOB. Methods The circulating cooling water in a refinery was simulated, and the morphology of corrosion products and the corrosion mechanism of electrochemical of 2507 duplex stainless steel in circulating cooling water simulated solution containing SRB+IOB were analyzed by SEM, EDS and electrochemical impedance spectroscopy (EIS) and polarization curves after soaking for different days. Results The corrosion rate of 2507 duplex stainless steel was very low, belonging to mild corrosion. Anodic polarization curves of 2507 duplex stainless steel in circulating cooling water simulated solution showed significant passivation regions and the passivation film had a good self-healing ability. With increasing corrosion time, the corrosion tendency first increased and then decreased while the corrosion rate first decreased and then increased. Conclusion The main cause for the pitting corrosion was the synergic effect of the surface adsorbed SRB and IOB as well as their metabolic activities with Cl-. 2507 duplex stainless steel had a good passivation performance and resistance to microbiological corrosion.