The MIC behavior of 2205 duplex stainless steel (2205 DSS) caused by the marine Pseudomonas aeruginosa (P. aeruginosa) with different soaking time was investigated through electrochemical testing techniques. Results show that the surface of 2205 DSS plate presents a microstructure composed of continuous ferrite matrix with uniformly distributed elongated islets of austenite phase with (111) preferred orientation. The open circuit potential E_OCP, polarization resistance (R_p), and charge transfer resistance (R_ct) measured in the sterile medium were larger than those in the P. aeruginosa inoculated medium during the whole soaking period of 7 d, indicating that P. aeruginosa accelerated the corrosion of 2205 DSS; The maintaining passivity current density (i_p) of the 2205 DSS increases with the immersion time in both sterile and P. aeruginosa inoculated medium, whilst, the value of which during immersion in the bacterial solution was higher than that in the sterile solution for 1 d, 3 d, and 7 d respectively, the fact further proved that P. aeruginosa accelerated the corrosion process of 2205 DSS; Scanning electron microscopy (SEM) results show that the amount of bacteria adhering to the steel surface gradually increased with the immersion time in the bacteria solution. After soaking for 3 days, the bacteria on the steel aggregated to form small clusters, and the bacteria aggregated to form a bacterial biofilm after 7 days. The bacterial biofilm accelerates the occurrence of pits, and later resulting in severe localized corrosion. X-ray photoelectron spectroscopy (XPS) results revealed that the water soluble CrO₃ could form on the 2205 DSS surface in the P. aeruginosa inoculated medium, which may be the inducement responsible to the MIC related pitting corrosion.