Abstract: TiO₂-Al₂O₃ composite supports were prepared by co-precipitation method and characterized by N₂ physisorption, X-ray diffraction (XRD) and pyridine adsorption FT-IR spectroscopy. Ni-Mo-S/TiO₂-Al₂O₃ supported catalysts were prepared with in-situ sulfidation method and their hydrodeoxygenation (HDO) properties were tested using phenol as model compound. The effects of aluminum sources and precipitants on the properties of TiO₂-Al₂O₃ composite supports and the effects of support properties on the HDO properties of Ni-Mo-S/TiO₂-Al₂O₃ catalysts were studied. The results showed that the pore volume and average pore diameter of the support prepared using aluminum chloride as aluminum source were as high as 1.12cm³/g and 18.0nm, respectively. The support prepared using aluminum sulfate and ammonium bicarbonate as initial materials had high specific surface area (295m²/g). Among three precipitants, the support precipitated using ammonia solution had the most L-acid sites while the support prepared using aluminum sulfate had a little of B-acid sites. The primary factors of supports which affected the HDO properties of Ni-Mo-S/TiO₂-Al₂O₃ catalysts were the acidity and specific surface area of supports. In the HDO of phenol on Ni-Mo-S/TiO₂-Al₂O₃ catalyst, the conversion, the deoxygenation reaction rate and the total oxygen-free compound were as high as 81.9%, 79.4% and 100%, respectively.