Abstract: The NiMo catalysts were prepared using the mechanical ball milling method, and their structures were characterized by XRD and XPS to investigate the effects of the Ni/(Ni+Mo) ratio on catalyst composition and structure, as well as the performance of phenanthrene hydrogenation. The results show that the catalysts prepared by this method have good dispersion of active components Ni and Mo, and are mesoporous catalysts with a concentrated pore size distribution in the range of 2−10 nm. The specific surface area and Mo^IV content of the catalysts increase first and then decrease as the Ni/(Ni+Mo) ratio increases, both reaching maximum values at 0.33. The moderate amount of Ni promotes Mo sulfidation to form the NiMoS active phase, while the excessive amount of Ni forms Ni_xS_y, which covers active sites and reduces the hydrogenation activity. When the Ni/(Ni+Mo) ratio maintains at 0.33, the specific surface area of the catalyst decreases as Ni and Mo content increases, while Mo^IV content shows an increase trend. Raising the amount of sulfurizing agent ammonium thiosulfate (ATS) could increase both the specific surface area and Mo^IV content of the catalyst. It is observed that the effect of the Ni/(Ni+Mo) ratio on phenanthrene conversion is consistent with the Mo^IV content of catalyst, and the maximum value of 74.7% is obtained at the Ni/(Ni+Mo) ratio of 0.33. This further rises to 96.5% when the Ni and Mo contents and S/Mo ratio increase to 4.8%, 16% and 4.5, respectively. Meanwhile, the total selectivity and yield of octahydrophenanthrene and perhydrophenanthrene reach 83.9% and 80.9%, respectively. Furthermore, perhydrophenanthrene is mainly formed by hydrogenation of side ring of phenanthrene.