Al2O3-TiO2 and Al2O3-TiO2-SiO2 (denoted as AT and ATS) composite oxides were synthesized by the sol-gel method, which were used as supports for bimetallic Pt-Pd catalysts. The typical physicochemical properties of the catalyst samples were characterized by means of N-2 adsorption, UV-vis diffuse reflectance spectroscopy (DRS), and X-ray diffraction (XRD). The diesel hydrodearomatization (HDA) and hydrodesulfurization (HDS) activities of the catalysts were evaluated using a microreactor system. In comparison to the Pt-Pd/AT catalysts, all of the Pt-Pd/ATS catalysts showed much higher HDA activities. A 100 It test showed that the Pt-Pd/ATS catalyst had a high equilibrium HDA activity, with 432 ppm sulfur diesel. The enhanced HDA activity and sulfur tolerance of Pt-Pd/ATS were likely attributed to the incorporations of Ti and Si into Al2O3, which optimized the interaction between the catalyst support and active metals.