The　gold　atoms　on　the　Au-20　cluster　had　been　substituted　by　the　palladium　and　platinum　atoms　to　obtain　the　doped　clusters　with　more　stable　geometries　as　a　function　of　the　bind　energy　and　interaction　energy　in　the　previous　study.　Therefore,　we　investigated　the　catalytic　activities　of　the　Au19Pd　and　Au19Pt　clusters　for　CO　oxidation　along　the　Langmuir-Hinshelwood　mechanism.　It　is　found　that　the　coadsorption　of　CO　and　O-2　on　the　doped　clusters　is　obviously　stronger　than　on　the　Au-20　cluster,　especially　on　the　doped　atom,　which　makes　potential　energy　of　the　transition　state　lower　than　the　total　energy　of　the　reactants　so　that　it　can　promote　CO　oxidation.　The　reaction　on　these　doped　clusters　with　the　heteroatom　on　the　vertex　is　more　difficult.　However,　the　Au19Pd　(S)　is　more　prone　to　catalyzing　the　CO　oxidation,　in　which　the　rate-limiting　step　has　the　lower　energy　barrier　of　38.84　kJ/mol　for　this　study.　Therefore,　the　single　atom　can　be　modified　to　change　the　catalytic　activity　of　the　cluster　for　the　CO　oxidation.　Meanwhile,　the　different　sites　on　the　clusters　have　different　strengths　of　activity　for　the　reaction.