CeO2　was　employed　to　modify　the　Cu/SiO2　catalyst　for　water-gas　shift　(WGS)　reaction,　and　two　different　ways　to　introduce　CeO2　were　applied,　i.e.,　ammonia　evaporation　hydrothermal　(AEH)　and　impregnation　(IM)　methods.　The　sizes　of　Cu　nanoparticles　and　strength　of　Cu-SiO2　synergetic　interaction　were　analyzed　by　HRTEM　and　H2-TPR　characterizations.　The　Cu+/Cu0　ratio　and　strength　of　Cu-CeO2　synergetic　interaction　were　evaluated　via　XPS　and　XAES　techniques.　It　was　revealed　that　more　Cu0　leads　to　higher　CO　conversion,　based　on　its　pronounced　effect　on　water　dissociation.　The　strength　of　the　Cu-SiO2　synergetic　interaction　in　the　Cu/SiO2　catalyst　varies　with　altering　the　state　of　CuO　species.　Cu-CeO2　synergetic　interaction　is　associated　with　oxygen　vacancies　in　CeO2,　which　also　act　as　active　sites　for　H2O　dissociation.　The　Cu/SiO2-CeO2-AEH　catalyst　exhibits　the　best　activity　and　stability　among　the　three　catalysts　toward　the　WGS　reaction,　because　it　has　a　large　number　of　Cu0　and　strong　synergetic　interaction　of　Cu　with　SiO2　and　CeO2.　©　2021　American　Chemical　Society.