Previous　QoS-aware　service　composition　methods　mainly　focus　on　how　to　generate　composite　service　with　the　optimal　QoS　efficiently　for　a　single　request.　However,　in　the　real　application　scenarios,　there　are　multiple　service　requests　and　multiple　service　providers.　It　is　more　important　to　compose　services　with　suboptimal　QoS　and　maintain　the　load　balance　between　services.　To　solve　this　problem,　in　this　paper,　we　propose　a　service　composition　method,　named　as　dynamically　change　and　balancing　composition　method　(DCBC).　It　assumes　that　the　QoS　of　service　is　not　static,　and　the　services　can　adjust　the　value　of　QoS　to　gain　more　opportunities　to　be　selected　for　composition.　The　method　mainly　includes　two　steps,　which　are　the　preprocessing　step　and　the　service　selection　step.　In　the　preprocessing　step,　a　backward　global　best　QoS　calculation　is　performed　which　regarding　the　static　and　dynamic　QoS　respectively;　then　guided　by　the　global　QoS,　the　feasible　services　can　be　selected　efficiently　in　the　service　selection　step.　The　experiments　show　that　the　DCBC　method　can　not　only　improve　the　overall　quality　of　composite　services　but　also　guarantee　the　fulfill　ratio　of　requests　and　the　load　balance　of　services.