In nature, microorganisms often adhere to the material surface to form biofilms, which affects the electrochemical process of the metal surface, thereby inducing microbiologically influenced corrosion. Biofilm is closely related to the occurrence of microbiologically influenced corrosion, and its structural composition and formation process have a great influence on the type and rate of corrosion reaction of metals. Due to the complexity of microbial activities and the lack of in-depth understanding of the interaction between biofilm and metal interface, the mechanism of microbiologically influenced corrosion is still unclear. Based on this, the mechanism of microbiologically influenced corrosion was discussed from the perspective of biofilm. The common bacteria that cause corrosion of materials, such as sulfate-reducing bacteria, sulfide-oxidising bacteria, iron-oxidizing bacteria, nitrate-reducing bacteria and other corrosive bacteria, were introduced, and their corrosion mechanisms were summarized. The characteristics, formation steps and dynamic evolution with time and external environment of the biofilm were comprehensively discussed. The factors affecting the formation and development of biofilms were emphatically discussed, including material factor and environmental factors, such as temperature, dissolved oxygen, pH, Cl-, Fe2+, flow velocity, nutrient media and magnetic field. Finally, considering the complexity of external factors, the problems in the process of biofilm research were expounded, and the importance of rational design of experimental schemes in the process of simulating biological environment was prospected.