The　possible　reaction　mechanisms　of　CH3O　and　CO　on　Pd　(111)　surface　were　studied　with　GGA-PW91　in　the　DMol3　software　package　based　on　density　functional　theory　(DFT).　The　relative　calculated　results　indicate　that　the　equilibrium　state　of　CH3O　adsorbed　at　fcc　position　is　the　most　stable　configuration　with　more　negative　charges　on　O　atom,　be　apt　to　be　attacked　by　electrophilic　reagents.　While,　CO　adsorbed　on　top　site　perpendicularly　by　the　interaction　between　C　atom　and　Pd　surface　has　lower　adsorption　energy,　and　its　carbon　atoms　will　possess　more　positive　charges,　which　avail　the　migration　for　electrophilic　insert　reaction.　Compared　with　CO　on　the　bridge　and　hollow　sites,　CO　adsorbed　on　the　top　sites　is　the　optimistical　configuration　for　the　coupled　reaction　yielding　CH3OOC,　which　may　be　attributed　to　the　mobility　and　electrophilcity　of　CO.