Abstract: Nowadays, deep hydrodesulfurization (HDS) of diesel fractions has become one of the most important approaches for production of clean fuels, as increasingly stringent quality standards of diesel fuel has been made all around the world. In the present work, operation conditions such as temperature, hydrogen pressure, liquid hourly space velocity (LHSV) and H2/oil volume ratio during the deep HDS of FCC diesel on an unsupported Ni-Mo-W catalyst were investigated, and activity of Ni-Mo-W catalyst was compared with a commercial NiMo/Al2O3 catalyst. The results show that reaction temperature, pressure, H2/oil ratio and LHSV made great influence on HDS efficiency of diesel fraction, and The reaction conditions of temperature 340 ℃, pressure 6.0 MPa, LHSV 1.5 h-1, and H2/oil ratio 600 were clarified to be the appropriate conditions for Shenghua FCC diesel hydrotreating on the unsupported Ni-Mo-W catalyst. The sulfur removal of the FCC diesel on the unsupported catalyst was 99.84%, and the nitrogen removal efficiency can reach up to 99.96%, much higher than that of the reference catalyst.