Abstract: The influenced corrosion behavior of Q235 carbon steel was investigated in the presence of Penicillium by using the surface analysis method,mass loss method,and electrochemical method.It is demonstrated that dense biofilms and depositing films of corrosion products form on the surface of Q235 carbon steel in the presence of Penicillium. Corrosion of Q235 carbon steel is evidently promoted and the corrosion morphology of Q235 carbon steel is pitting in Penicillium systems.The films on the surface of Q235 carbon steel changes through a complex process,from free state to solid state and single-layer to multilayer.The effect of the biofilm depends on bacterial activity,and the corrosion promotion of the biofilm decreases as the bacterial activity weakens.