Abstract: A series of ZrO₂-Al₂O₃ mixed oxides and Pd/ZrO₂-Al₂O₃ catalysts with various zirconium contents were prepared by the impregnation method. Hydrodesulfurization (HDS) reaction of thiophene over Pd/ZrO₂-Al₂O₃ catalysts was carried out in a flow reactor. XRD, TPR, H₂-TPD, NH₃-TPD and nitrogen adsorption techniques were used to characterize the samples. The result showed that the effect of zirconium content on HDS properties was observed over Pd/ZrO₂-Al₂O₃ catalysts. Introducing suitable zirconium into Pd/Al₂O₃ resulted in relatively higher dispersed-metal, more acid amount, more H₂ adsorbed amount and weaker metal-support interaction, and also leaded to the increase of the adsorption sites of thiophene and active centres, the decrease of the apparent activation energy, all of above mentioned factors were favorable for the HDS of thiophene. The maximum HDS activity was observed for Pd/ZrO₂-Al₂O₃ catalysts with zirconium content of 9%.