World-wide changes in clean gasoline requirements have recently increased the research work for reducing sulfur in cracked naphtha. In this work, the bifunctional catalyst Ni-Mo/HZSM-5 was prepared and was characterized by temperature-programmed desorption of NH3 (NH3-TPD), nitrogen adsorption (BET), FT-IR analysis with adsorbed pyridine as well as by X-ray powder diffraction analysis. NH3-TPD shows the presence of strong acid sites at about 430degreesC in HZSM-5 zeolite and the strong acid is weakened after the Ni-Mo incorporation. FT-IR analysis with adsorbed pyridine reveals that the L acid site in Ni-Mo/HZSM-5 enhances and the L and B acid sites in the inactive catalyst can be recovered by calcination at 500degreesC. Hydrodesulfurization of the cracked naphtha was carried out in a 100 mL fixed bed flow reactor and the effects of hydrogen pressure and reaction temperature on the activity of the catalyst were studied. It was revealed that the octane loss with certain HDS% of the hydrotreated naphtha can be reduced greatly in the hydrotreating process over Ni-Mo/HZSM-5 by selecting proper hydrogen pressure, reaction temperature and the content of Ni-Mo in the catalyst. (C) 2004 Elsevier B.V. All rights reserved.