XML　is　the　de　facto　standard　for　data　representation　and　exchanging　on　web.　The　query　processing　technique　of　XML　streaming　data　is　a　hotspot　in　current　research.　Focused　on　the　characteristics　of　processing　semi-structure　XML　streaming　data　such　as　the　stream　arriving　continuously,　requiring　to　be　read　sequentially　and　only　once　into　memory,　the　querying　must　be　processed　on　the　fly,　a　method　of　processing　XPath　query　based　on　forest　transducer　is　proposed.　Firstly,　conversion　rules　of　forest　transducer　are　defined　for　XPath　query.　And　then　the　transducer　is　driven　by　input　streaming　data　nodes.　Stack　and　abstract　syntax　tree　are　applied　to　implement　match　and　state　transformation　in　running　procedure.　The　relationships　between　state　functions　and　intermediate　results　are　kept　by　the　abstract　syntax　tree,　and　the　query　results　are　output　in　reducing　process.　Finally,　the　experimental　results　show　that　our　approach　is　effective　and　efficient　on　this　problem,　and　outperforms　about　30　percent　of　the　state-of-the-art　algorithms　especially　for　large　processed　data.　At　the　same　time,　memory　usage　is　nearly　constant.　This　method　resolves　the　balance　between　time　and　space　complexity,　and　it　is　a　useful　reference　for　other　methods.　©　2017　Totem　Publisher,　Inc.　All　rights　reserved.