Abstract: A series of iron sulfide catalysts were prepared in 5% H₂S/N₂ atmosphere at different pre-sulfidation temperatures, and their catalytic activity for naphthalene hydrogenation was studied at 360 ℃ in 1% H₂S/H₂ atmosphere at 5 MPa. The component transformation of the catalyst under varied pre-sulfidation temperature and reaction conditions was researched using MES, XRD and XPS. The results revealed that the sulfidation process was in the form of sulfurizing from surface to interior in the order of FeS₂→FeS, Fe_1–xS→Fe₃S₄→Fe₂O₃ during which transferring sulfur to the body phase was benefited from the rise of temperature. After contacting 1% H₂S/H₂ gas, the particles rapidly transformed to Fe_1–xS from outside to the inside. By adjusting sulfidation conditions, the Fe_1–xS content was high while the particle size was small, which made it possible to obtain the greatest activity of the catalyst.