In　this　article,　moisture-treated　Pd@CeO2/Al2O3　and　Pd/CeO2/Al2O3　catalysts　were　synthesized　and　applied　in　automotive　three-way　catalytic　(TWC)　reactions.　Compared　to　the　Pd/CeO2/Al2O3　catalyst,　the　Pd@CeO2/Al2O3　core-shell　catalyst　had　better　TWC　activities.　Transmission　electron　microscopy　(TEM)　images　and　X-ray　photoelectron　spectra　(XPS)　showed　excess　PdO2　on　the　Pd　and　CeO2　interface　of　Pd@CeO2　nanoparticles.　Fourier　transform　infrared　(FT-IR)　spectra　analysis　demonstrated　the　generation　of　the　hydroperoxyl　(*OOH)　groups　on　the　surface　of　the　Pd@CeO2　nanoparticle.　CO-diffuse　reflectance　Fourier　transform　(DRIFT)　measurement　suggested　that　the　CO　adsorbed　on　*OOH　species　contributed　to　the　formation　of　CO2　and　intermediate　*COOH.　NO-DRIFT　results　showed　that　more　*NO2　species　appeared　on　the　moisture-treated　Pd@CeO2　nanoparticle,　which　was　the　main　active　site　in　the　automobile　TWC　reaction.　These　were　the　main　factors　contributing　to　the　moisture-treated　Pd@CeO2/Al2O3　catalyst＇s　high　catalytic　activities.　The　collected　data　revealed　the　crucial　role　of　the　co-promoting　effect　of　moisture　and　core-shell　interface　on　TWC　reactions　over　the　Pd@CeO2/Al2O3　catalyst,　which　could　be　applied　to　other　catalytic　reactions.