One　of　the　important　issues　with　the　scandate　cathode　is　the　mechanism　by　which　Sc　works　on　the　cathode　surface.　A　surface　Sc-rich　dispenser　cathode　was　prepared　via　the　vacuum　evaporation　method　to　clarify　the　role　of　Sc　in　the　cathode　performance.　The　XPS　results　indicate　that　the　surface　chemical　state　of　Sc　on　the　surface　after　activation　is　consists　of　Sc-0　and　Sc　epsilon+　(0＜epsilon＜3).　Furthermore,　the　adsorption　energy,　the　work　function,　charge　density　difference,　polarization　effect　and　dipole　moment　of　the　Ba-x-O-y　adsorbed　on　the　Sc　surface　were　calculated　by　means　of　first-principles　calculations.　The　results　show　that　the　work　function　of　the　Bax-Oy　dipole　adsorbed　on　the　Sc　is　1.9-2.8　eV　with　the　average　value　of　2.262　eV,　which　is　consistent　with　the　experimentally　measured　result.　The　work　function　of　Ba-x-O-y　adsorbed　Sc　(002)　gets　to　the　lowest　at　a　coverage　of　25　%O-25　%　Ba.　The　change　of　dipole　moment　due　to　polarization　and　charge　transfer　in　the　adsorbed　layer　could　affect　the　work　function.