The　reaction　behavior　of　CO　over　Au/TiO2　has　been　investigated　by　a　temperature-programed　surface　reaction　(TPSR)　testing.　We　have　found　that　there　maybe　existed　four　reaction　processes　of　oxidizing　CO　over　Au/TiO2　in　the　O-2-poor　stream　containing　a　trace　H2O　at　or　below　80　degrees　C:　(i)　CO　adsorbed　at　TiO2　sites　is　oxidized　by　H2O　to　form　Ti-COOH　species　below　80　degrees　C,　which　is　desorbed　into　CO2　and　H2O　at　80　degrees　C;　(ii)　CO　adsorbed　at　Au　sites　is　oxidized　by　H2O　to　form　CO2;　(iii)　CO　adsorbed　at　Au　sites　is　oxidized　by　H2O　to　form　H-2　and　CO2　according　to　the　water-gas　shift　reaction,　which　only　occurs　with　the　desorption　of　Ti-COOH　species　at　TiO2　sites　into　CO2　at　80　degrees　C;　(iv)　CO　adsorbed　at　Au　sites　is　oxidized　by　molecular　O-2　to　form　CO2.　For　the　three　processes　of　H2O　oxidizing　CO,　the　chemisorption　result　of　CO　and　O-2　over　Au/TiO2　shows　that　it　may　be　the　Ti-bonded　hydroxyl　species　(Ti　OH)　but　not　the　adsorbed　molecular　H2O　at　TiO2　sites　to　react　with　CO　adsorbed　at　Au　or　TiO2　sites.　For　the　process　of　O-2　oxidizing　CO,　the　non-promotion　of　pre-adsorption　of　O-2　on　the　formation　of　CO2　below　80　degrees　C　indicates　that　it　may　be　the　physisorbed　molecular　O-2　not　the　chemisorbed　O-2　to　directly　react　with　CO　adsorbed　at　Au　sites.　This　work　also　indicates　that　the　process　of　CO　oxidation　in　the　presence　of　H2O　over　the　supported　Au　catalyst　may　be　simultaneously　oxidized　by　O-2　and　H2O　according　to　the　respective　process.　(C)　2013　Elsevier　Inc.　All　rights　reserved.