A series of Ni/HZSM-5 bifunctional catalysts were prepared and were characterized by infrared spectroscopy of adsorbed pyridine as well as by X-ray powder diffraction analysis. The activity of the catalysts was investigated in hydrogenation and aromatization for the hydrotreating of cracked naphtha. It was revealed that the aromatization activity of the Ni/HZSM-5 catalyst decreases with the increase of catalyst acidity. The production of aromatics in hydrotreated naphtha with relatively low reaction temperature is related to a complicated scheme of carbenium ion reactions taking place on the catalyst surface and which are associated with the cooperation of the L acid site and the B acid site in the catalyst. The experimental results of hydrotreating of FCC naphtha show that the Ni/HZSM-5 catalyst has high aromatization and moderate hydrogenation activities; with the increase of reaction temperature the RON of the hydrotreated naphtha increases, mainly because of the production of aromatics, but at the same time there is a decrease of the total naphtha yield, because of the production of light products.