Abstract: The uniform corrosion and pitting corrosion behavior of J55 steel was studied in oil field simulated produced water without scale inhibitor and CO₂, with CO₂, with scale inhibitor and with both scale inhibitor and CO₂ through immersion corrosion and electrochemical corrosion tests. The results show that under the condition without scale inhibitor and CO₂, the uniform corrosion rate of J55 steel was relatively low, and the maximum pitting corrosion rate was the highest. Compared to those without scale inhibitor and CO₂, the uniform corrosion rate of the steel increased and the maximum pitting corrosion rate decreased under the condition with CO₂, and both decreased under the condition with scale inhibitor. Under the condition with both CO₂ and scale inhibitor, the uniform corrosion rate of the steel was the highest, and the maximum pitting corrosion rate was lower than that without scale inhibitor and CO₂. When CO₂ was present in the system, CaCO₃ or CaMg(CO₃)₂ scaling products were mainly formed on the surface of the steel. Under the condition with both CO₂ and scale inhibitor, scale inhibitor would inhibit the scaling process, change the structure of corrosion products and scale deposits, and lost the protective effect on the matrix.