Composite　service　can　be　scheduled　and　executed　around　trust　degree　of　services　through　introducing　trust　degree　as　the　accord　of　service　scheduling　and　execution.　Higher　trust　degree　services　can　join　into　service　composition　and　the　trustiness　of　composite　service　can　be　improved.　Trust　is　introduced　into　service　composition　and　trust　enhanced　service　composition　schedule　problem　is　discussed.　The　mathematic　model　of　scheduling　problem　is　proposed　and　the　ant　colony　system　based　scheduling　algorithm　is　designed.　The　scheduling　algorithm　has　good　performance　through　analysis　of　experimental　results.