Abstract: CoMo/γ-Al₂O₃ catalyst for hydrodesulfurization (HDS) were prepared by equal volume impregnation method with and without the presence of pulsed electronmagnetic field (PEMF). Experimental results revealed that the catalyst prepared by PEMF with a voltage of 200 V exhibited higher catalytic activity for hydrodesulfurization of thiophene, 2-methythiophene and benzothiophene than the catalyst prepared by conventional impregnation. The surface morphology and physico-chemical properties were characterized by using BET, XRD, H₂-TPR and TEM techniques, respectively. The results showed that appropriate PEMF treatment promotes the active component dispersion on the γ-Al₂O₃ surface by interacting with the charged particles in reaction system. The interaction between the support and the active species MoO₃ is weakened and thus facilitates the reduction of the catalyst and the formation of CoMoS active phase.