Cu-SAPO-18 molecular sieve was synthesized and a series of CuZ-Ce-n catalysts with thin CeO2 film on the external surface of Cu-SAPO-18 were prepared by the means of liquid deposition. The thickness of CeO2 film was controllably tuned, and the different film thickness significantly influenced the catalytic activities of CuZ-Ce-n catalysts for NH3-SCR reaction. The protection of CeO2 thin film not only inhibits the active sites from aggregating into copper oxides at high temperature, but also suppresses H2O from competitively adsorbing on the acid sites and Cu active sites over CuZ-Ce-n catalysts. Thus CuZ-Ce-n catalysts exhibit preferable resistance to H2O. Moreover, CeO2 thin film can suppress the formation and deposition of sulfate species from blocking the active sites over CuZ-Ce-n catalysts. It leads to that CuZ-Ce-n catalysts possess the higher SO2 resistance than Cu-SAPO-18.