The in-situ hydrodesulfurization(HDS) reaction of thiophene was performed by using hydrogen which was generated by a water gas shift reaction(WGSR) in a same catalyst bed. The catalyst used was commercial CoMo/Υ-Al₂O₃ and it was used after presulfiding. The activity in the conversion of thiophene by using hydrogen generated in-situ from a WGSR was inferior to that by the pure hydrogen. The lower efficiency in the in-situ HDS with WGSR was attributed to water, carbon monoxide and carbon dioxide which were mixed after WGSR. The following rate equation, which was revised from that of Satterfield, was proposed for this in-situ HDS reaction of thiophene with WGSR to explain the observed phenomena. -r_HDS = kK_HK_TP_HP_T / (1+K_HP_H+K_TP_T+K_H2OP_H2O+K_COP_CO+K_CO2P_CO2+K_SP_S)² The experimental results were in good accordance with this equation. The active sites for both WGSR and HDS were ascribed to the prohibition of competitive adsorptions.