Abstract: In oil-immersed transformers, sulfur corrosion of copper windings produces Cu₂S, leading to a series of performance degradations in both insulating paper and insulating oil, which seriously threatens the normal operation of oil-immersed transformers. With regard to sulfur corrosion of copper windings, relevant researches are reviewed from the following four aspects: sources of corrosive sulfur, mechanisms of sulfur corrosion and its influencing factors (including environmental conditions and copper winding characteristics), hazards of sulfur corrosion to equipment, and primary inhibition and protection measures.