Abstract: The effects of Cr₂₃C₆ precipitates and Al₂O₃ inclusions on the corrosion resistance of L80-9Cr steel were studied by electrochemical test and FeCl₃ pitting test. The results show that the precipitation and aggregation of Cr₂₃C₆ in the original martensitic lath bundles increased the degree of lattice distortion at the small-angle grain boundaries, making it have higher electrochemical activity and reducing the corrosion resistance of the material. On the other hand, the precipitation of Cr₂₃C₆ led to the formation of the surrounding Cr-depleted area, which increased the tendency of pitting corrosion of the material. In addition, the existence of Al₂O₃ inclusions also provided a favorable position for the initiation and development of pitting corrosion, and the combined effect of the two led to the severe pitting corrosion of L80-9Cr steel.