Abstract: A series of Ce-La/MgAl₂O₄-x catalysts were prepared by the incipient wetness impregnation method and characterized by BET, XRD, H₂-TPR, CO-TPR and in situ FT-IR. The results demonstrate that the catalyst with a Mg/Al molar ratio of 0.5 yields the most uniform dispersion of CeO₂ and greatly enhances formation of Ce-O-La solid solution, resulting in the increase of oxygen vacancy and surface Ce³⁺ content. Thereby, the synergistic effect between surface Ce³⁺ and oxygen vacancy gives rise to the best catalytic performance of NO reduction. Moreover, introduction of Mg species suppresses tranformation of CeO₂ to Ce(SO₄)₂/Ce₂(SO₄)₃ and then improves the SO₂ resistance performance of Ce-La/MgAl₂O₄-0.5.