Abstract: Binary-structured Al2O3 supports were prepared with sol-gel technique and Ni-Mo/Al2O3 catalysts were prepared by impregnation method with the modified supports. The HDS activity of the catalysts supported by sol-gel modified supports was evaluated in a fixed-bed micro-reactor under moderate-pressures. The results revealed that, the HDS activity of the catalysts on modified support with alumina sol was higher than that of catalysts on ordinary supports. The supports modified and the catalysts prepared were characterized by XRD, TEM and pyridine-IR. The XRD patterns and TEM results indicated that the alumina sol was present in phase of η-Al2O3 on the surface of supports and the η-Al2O3 particles were close to nanometer size. The pyridine-IR results indicated that the acidities (the Brönzed + Lewis) of the catalysts on modified supports are higher than those of the catalysts on ordinary supports. The HDS activities of the catalysts are increased due to the nanometer size of η-Al2O3 and the increase in acidic amounts of the catalysts.