The　possible　models　of　CO2B2　and　CO2B2Pt　alloy　clusters　supported　on　TiO2　surface　were　studied　by　the　density　functional　theory.　The　geometrical　optimized　results　indicated　that　CO2B2　and　CO2B2Pt　alloy　clusters　preferred　to　be　bound　on　the　top　of　the　two　O　atoms　of　TiO2　with　two　Co　atoms.　By　analyzing　the　partial　density　of　states　for　CO2B2　and　CO2B2Pt　alloy　clusters,　it　was　shown　that　the　bonding　interaction　between　partial　Co　and　B　is　enhanced　in　the　CO2B2　system.　For　the　CO2B2Pt　system,　the　bonding　interaction　between　Pt　and　B　is　also　enhanced.　In　these　systems,　new　molecular　orbitals　have　formed　after　CO2B2Pt　alloy　clusters　were　supported　on　TiO2　surface.　Comparing　the　results　of　CO　and　O2　adsorption　on　PtCO2B2/TiO2　and　CO2B2/TiO2　surfaces,　it　was　concluded　that　the　promotion　of　CO　and　O2　adsorption　on　the　CO2B2　is　due　to　the　Pt　atoms　onto　the　cluster.