Abstract: For the deep desulfurization of gasoline，it is crucial to avoid the decreases of octane number (RON) and final gasoline yield; for the deep reduction of sulfur content in diesel oil，the major difficulties are how to remove sulfur from inactive compounds like 4,6-dimethyldibenzothiophene (4,6-DMDBT) and at the same time to conquer the inhibiting effects of polyaromatics and nitrogen compounds in the feed as well as H2S produced during the desulfurization. In this paper，the progresses of the development of deep hydrodesulfurization (HDS) catalysts for commercial application as well as the fundamental researches on HDS catalysis and reaction mechanism were reviewed. It was then emphasized that having an insight into the catalyst structures and HDS reaction mechanism on atomic or molecular levels played an important role in the design of highly active and selective catalysts of the next generation.