A series of alumina with different crystal structures from gamma-Al2O3 to theta-Al2O3 has been synthesized by precipitation method using aluminum nitrate and aluminum chloride hexahydrate, and the corresponding NiMo/Al2O3 catalysts were prepared based on above different alumina. The typical physic-chemical properties of the supports and series catalysts were characterized with XRD, BET, UV-Vis DRS, Py-IR, Raman and XPS characterization methods, and their catalytic activities were tested for FCC diesel hydrodesulfurization. The catalytic system was tested in hydrodesulfurization reactions of FCC diesel under atmospheric and high pressure (5 MPa). The NiMo/delta-Al2O3 catalyst prepared by aluminum nitrate exhibited the highest HDS and HDN efficiencies, 99.4% and 993% respectively, which were mainly ascribed to the concentrated pore size distribution, moderate MSI and higher degree of sulfidation. (C) 2016 Elsevier B.V. All rights reserved.