The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efifcient NiMo/Al2O3 hydrodesulfurization (HDS) catalysts. At ifrst, ifve typical impregnating solutions were designed; the existing metal precursors, such as [Mo4(citrate)2O11]4--like, [P2Mo18O62]6--like and [P2Mo5O23]6--like species in the solutions were con-ifrmed by laser Raman spectroscopy (LRS). The UV-Vis spectra results indicated that the solutions containing both phos-phoric acid and citric acid could change the existing form of nickel species. Five corresponding NiMo/Al2O3 catalysts were prepared by the incipient wetness impregnation method. The LRS analysis results of dried catalysts showed that the above metal precursors could be partly retained on alumina support after impregnation and drying, although the interface reaction between different metal precursors and alumina support unavoidably took place. Then the catalysts were sulifded and char-acterized by N2 physisorption, TEM and XPS analyses. The results showed that different metal precursors in impregnating solution could mainly result in the difference in both the morphology of (Ni)MoS2 slabs and the promoting effect of Ni spe-cies. The catalyst prepared mainly with [P2Mo5O23]6--like species used as precursors exhibited worse dispersion of (Ni)MoS2 slabs and lower ratio of Ni–Mo–S active phases than the one with [Mo4(citrate)2O11]4--like species. Promisingly, the catalyst prepared with co-existing [Mo4(citrate)2O11]4--like, [P2Mo18O62]6--like and [P2Mo5O23]6--like species showed better hydrode-sulfurization activity for 4,6-DMDBT thanks to its more well-dispersed Ni–Mo–S active phases.