Abstract: The catalyst precursors for slurry-bed hydroprocessing of residue need to be sulfurized for higher catalytic activity. In this study, two of the most important precursors described above, ammonium molybdate and nickel nitrate, are sulfurized. Sodium sulfide is employed as the sulfrization reagent and ammonium chloride is employed as the auxiliary sulfurization reagent. The sulfruization is carried out in three stages: Stage 1. Precursors are sulfurized directly in water-solution; Stage 2. Precursors are sulfurized in water-oil emulsification; Stage 3. The sulfurized catalysts, which have been dispersed in the media, are heated in the presence of hydrogen. XRD is employed to recognize the crystalline components in the sulfurization products, and the crystal-grain size is calculated using Scherrer's equation. TEM is employed to observe the form and size of the particles of the products. It is observed that nickel nitrate is transferred into micro-crystallized NiS2 firstly, and crystallized to NiS and Ni7S6 after heated under hydrogen, with little change in particle sizes and crystal-grain sizes; while molybdate is transferred into crystallized thioxomolybdate before the heating, and micro-crystallized MoS2 finally, with great increase in their particle sizes and great decrease in their crystal-grain sizes, thus it can be concluded that the heating under hydrogen is an important stage in the sulfurization of both precursors. According to the result of XRD, the addition use of ammonium chloride in sulfurization does not affect the chemical composition, the particle size or the crystalline-grain size of the sulfurized product of nickel salt. But the molybdate cannot be sulfurized at all without the existence of NH4Cl. When the amount of NH4Cl added rises up, it is shown by XRD that its chemical composition does not vary much, but the crystalline size is slightly decreased, and the particle of the product turns to be larger and looser. The viscosity and density of the dispersion media affect the particle size and the crystalline-grain size of the sulfurization products remarkably. When the Kelamayi vacuum residue, which has a higher viscosity and density, is used as the dispersion media, the crystalline-grain size is smaller than that of the lubricant used as the dispersion media and the shape of the particles turns from compact to loose.