The　improved　grey　target　theory　is　applied　in　the　research　of　transformer　oil-paper　insulation　aging　state.　First　the　data　are　measured　by　recovery　voltage　method　and　relative　parameters　are　identified　by　equivalent　circuit　of　ED,using　extracted　parameters　as　the　characteristic　quantity　of　assessment　of　oil-paper　insulation　aging　state.　Second,because　of　the　different　influence　of　several　characteristic　quantities　on　oil-paper　insulation　aging　state,the　im-　proved　AHP　method　and　entropy　weight　method　is　used　in　the　weight　distribution　of　these　characteristic　quantities.　Last,the　data　of　transformer　are　collected　and　grades　of　oil-paper　insulation　aging　states　are　calculated.　Experimental　results　show　that　this　method　can　effectively　and　reasonably　evaluate　the　transformer　oil　paper　insulation　aging　status　andprovideareferenceforthetransformerconditionmaintenance.　©　2018,　Xi＇an　High　Voltage　Apparatus　Research　Institute　Co.,　Ltd.　All　right　reserved.