Claus reaction was applied for the selective removal of H2S contained in the gasified coal gas and the characteristics of Claus reaction over the Ce-based catalysts were investigated to propose the reaction mechanism in this study. The Ce-based catalysts showed the high activities on Claus reaction. Specially, Ce0.8Zr0.2O2 catalyst had a higher activity than CeO. On the basis of our expeimental results, it was proposed that the selective oxidation of H2S was carried out by the lattice oxygen in the Ce-based catalysts and that the reduction of SO2 was performed by the lattice oxygen vacancy in the reduced catalyst. Since the mobility of the lattice oxygen in Ce0.8Zr0.2O2 composite catalyst was better than the one in CeO2, Ce0.8Zr0.2O2 provided more lattice oxygen for the selective oxidation of H2S. Claus reaction over the Ce-based catalysts was carried out by the redox mechanism.