Abstract: SiO₂-Al₂O₃, with a mass content of 5%, 10% and 15%, was synthesized by using a Al(NO₃)₃-NaAlO₂ double hydrolysis method, with surfactant Pluronic P₁₂₃ as template and Si(OC₂H₅)₄ as Si source. The Co-Mo/SiO₂-Al₂O₃ hydrotreating catalysts for lubricating oil were then prepared by co-impregnation method and characterized by a series of techniques such as XRD, N₂ sorption, Py-FTIR, NH₃-TPD, H₂-TPR, TEM and XRF. The results show that the SiO₂-Al₂O₃ support containing 10% Si is provided with abundant moderate-strong acid sites and partially ordered mesoporous structure; MoS₂ particles are uniformly dispersed on the SiO₂-Al₂O₃ surface. Moreover, the Co-Mo/10%SiO₂-Al₂O₃ catalyst exhibits high amount of Bronsted acid sites and type Ⅱ CoMoS active phase. The catalytic performance was evaluated in a high-pressure fixed-bed reactor, with second vacuum side distillate oil as the raw material oil. The results show that the Co-Mo/10%SiO₂-Al₂O₃ catalyst exhibits high activity in hydrotreating and paraffins and cycloalkanes are the main components in product oil. Under 380℃, 15 MPa, a space velocity of 0.6 h^-1, and a hydrogen to oil ratio of 1000, the HDS and HDN values over Co-Mo/10%SiO₂-Al₂O₃ exceed 99%. Meanwhile, the contents of S and N in the product are less than 10 and 2 μg/g, respectively, which can meet the requirements on the raw materials for the subsequent isomerization dewaxing process.