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Composite materials (AZ-x) were prepared by mixing the nanosized HY zeolite and γ-Al2O3 using the sol-gel mixing method and were employed as the support for NiMo catalysts (NiMo/AZ-x). These composites and catalysts were characterized by XRD, BET, TPD, TPR, HRTEM and FT-IR spectroscopy. Compared with the NiMo catalyst supported onγ-Al2O3 (NiMo/γ-Al2O3), these NiMo/AZ-x catalysts show higher activity in the hydrodesulfurization (HDS) of FCC diesel, and the HDS activity increases with an increasing HY mass content in the composites, provided that the HY mass fraction does not exceed 20％. Compared with γ-Al2O3, the introduction of nanosized HY zeolite can improve the porous structure of the composites, which can benefit the mass transfer of the reactant molecules. Furthermore, the nanosized HY zeolite in the composites can modify their surface properties which would increase the ratio of metal species to be transformed into reducible phase in low temperature region and modify the morphology of the MoS2 phases to form more multi-stacked MoS2 active phases with increased dispersion of edges and cers of Mo atoms.