Adsorption　of　CH3O　at　four　sites　(top,　bridge,　hcp,　fee)　on　Au(111)　surface　has　been　investigated　by　density　functional　theory　method　at　the　generalized　gradient　approximation　level.　We　have　performed　calculations　on　adsorption　energies,　structures,　Mulliken　charges　and　vibrational　frequencies　of　CH3O　on　Au(111)　surface　with　full-geometry　optimization.　The　predicted　results　are　compared　with　the　available　experimental　observation.　The　calculated　CH3O　adsorption　structure　and　stretching　vibrational　frequencies　agree　well　with　experimental　ones,　and　precise　determinations　of　adsorption　sites　are　carried　out.　The　most　favorite　adsorption　on　Au(111)　occurs　at　the　bridge　site,　and　O-C　axis　is　tilted　to　the　surface.　However,　on　hollow　sites　(hcp,　fcc)　the　species　is　adsorbed　in　an　upright　geometry　(pseudo-C-3v　local　symmetry).