Abstract: The corrosion behavior of Q355NHq steel with four rare earth concentrations in simulated marine atmosphere environment was studied by salt spray corrosion test and electrochemical test. The morphology and composition of two typical inclusions in the steels in Cl^--containing environment were studied by in-situ immersion test. The results show that when the mass fraction of rare earth elements was 0.017%, the corrosion rate of the sample was the smallest, and the content of α-FeOOH in the rust layer was the highest after 24 hours of salt spray test. With the increase of rare earth concentration in the steel, the charge transfer resistance R_ct increased first and then decreased. When the mass fraction of rare earth elements was 0.017%, the corrosion current density of the sample was the smallest and the R_ct value was the largest, which was about 3 934 Ω·cm². After soaking in Cl^--containing environment, RE_xO_y inclusions in the steel modified by rare earth showed better corrosion resistance than CaS-Al₂O₃ inclusions.