The　aging　feature　quantity　of　transformer　oil-paper　insulation　system　is　different　under　different　test　methods.　Some　ambiguity　and　uncertainties　still　exist　in　the　comprehensive　assessment　of　complex　insulation　condition.　Thus,　the　transformer　oil-paper　insulationcondition　assessment　model　is　established　based　on　fuzzy-gray　clustering　and　comprehensive　weight　method.　Firstly,　the　aging　index　hierarchical　graph　based　on　multiple　test　methods　is　obtained.　Usingfuzzt　C　-means　clustering　(FCM,　Fuzzy　c-means),　the　four　levels　of　the　aging　state　standard　index　vector　table　of　oil-paper　insulation　condition　assessment　is　identified　and　the　threshold　of　whitening　function　is　determined　with　the　collected　transformer　insulation　aging　index　data.　Secondly,　the　gray　clustering　coefficient　is　calculated　by　assigning　weight　to　the　aging　quantity　by　weighting　method　combined　with　subjective　and　objective　sense.　Thirdly,　a　comprehensive　assessment　model　of　oil-paper　insulation　state　is　built　taking　the　grade-one　gray　clustering　coefficient　as　the　membership　matrix　of　grade-two　fuzzy　comprehensive　assessment.　Finally,　the　validity　and　accuracy　of　new　assessment　method　are　verified　by　examples,　which　shows　a　good　prospect.　©　2017,　Science　Press.　All　right　reserved.