Herein, we designed and constructed a mesoporous LaAlO_x via a solvent evaporation induced self-assembly protocol. The structure and physicochemical property of the corresponding NiMo supported catalyst was analyzed by a set of characterizations, and its catalytic activity was investigated for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene. It has confirmed that the incorporation of La profoundly facilitate the generation of “Type Ⅱ” NiMoS phase by weakening the interaction of Mo–O–Al leakage and promoting the sulfidation of both Ni and Mo oxides as well as changing the morphology of Ni promoted MoS₂ slabs, thereafter boosting the HDS performance substantially. The finding here may contribute to the fundamental understanding of structure-activity in ultra-deep desulfurization and inspire the advancement of highly-efficient HDS catalyst in future.