Abstract: Mesoporous MoO₃-ZrO₂ composite oxides were prepared by sol-gel method. The influence of the mass ratio of MoO₃/ZrO₂ on the crystal phase, specific surface area, pore size and morphology characteristics were investigated. The synthesized composite oxides were characterized by XRD, BET, SEM and FT-IR. With FCC gasoline fraction as the raw material, the catalytic activity was evaluated by hydrodesulfurization reaction after the prevulcanization of the composite oxides. The results show that the ZrO₂ containing MoO₃ had less monoclinic phase than ZrO₂ and mainly existed in stable tetragonal phase. The appropriate improvement of the mass ratio of MoO₃/ZrO₂ were beneficial to the increase of specific surface area and average pore size. The excessive mass ratio of MoO₃/ZrO₂ depressed the formation of mesopores and produced a new type chemical bond and a small amount of Zr(MoO₄)₂ crystal phase. When the mass ratio of MoO₃/ZrO₂ was 30%, the worm structure appeared on the surface of ZrO₂, and the desulfurization rate reached its maximum. Thus, the appropriate improvement of the mass ratio of MoO₃/ZrO₂ could obtain a higher desulfurization rate.