Résumé : The biofilm of Bacillus cereus on the surface of X80 pipeline steel was investigated from forming to shedding. Based on the observed biofilm morphology and pit analysis, it was found that B. cereus biofilm could stimulate X80 pipeline steel pitting corrosion, which was attributed to the nitrate reduction of bacteria beneath the biofilm. Electrochemical measurements and general corrosion rate results showed that B. cereus biofilm can better accelerate X80 pipeline steel corrosion compared to sterile solutions. Interestingly, the results also showed that thick biofilms had a slight tendency to inhibit the general corrosion process compared with its formation and exfoliation, which was confirmed by scanning Kelvin probe. The corrosion rate of X80 pipeline steel in artificial Beijing soil is closely related to the state of the biofilm, and nitrate reducing bacteria accelerates the occurrence of pits. The corresponding corrosion mechanisms are proposed.