Abstract: Molybdenum disulfide was prepared from ammonium tetrathiomolybdate as a precursor. Ni-Mo-S catalyst was also synthesized from ammonium tetrathiomolybdate with nickel as a promoter. The hydrodesulfurization (HDS) performance of these two catalysts were studied using a model fuel of decalin solution containing 0.8% DBT with and without quinoline in it. The results indicate that the introduction of nickel increases the HDS activity of molybdenum disulfide. The existence of quinoline restrains the HDS activities of these two catalysts. Both the activities of the hydrogenation pathway (HYD) and direct desulfurization (DDS) are suppressed for the molybdenum disulfide catalyst in case of the presence of quinoline. When quinoline exists, the DDS activity is enhanced on Ni-Mo-S catalyst and the HYD activity is just the other way. The inhibiting effect on HYD activity for Ni-Mo-S catalyst is significantly weaker than molybdenum disulfide, indicating that the introduction of nickel increases the nitrogen resistance of molybdenum disulfide.