To　achieve　the　goal　of　＇carbon　peaking　and　carbon　neutrality＇,　the　construction　of　a　new　power　system　has　become　an　inevitable　trend　of　power　grid　development.　Given　this,　it　is　of　great　significance　to　ensure　the　reliable　operation　of　power　transformers.　Thus　an　evaluation　method　of　the　oil-paper　insulation　condition　of　a　transformer　based　on　fuzzy　K　nearest　neighbor　and　evidence　theory　is　proposed.　First,　a　multi-characteristic　parameter　database　is　constructed,　and　the　basic　probability　allocation　method　of　evidence　is　proposed　based　on　the　database.　Then,　a　combination　weighting　method　is　used　to　synthesize　the　subjective　and　objective　weights　of　the　characteristic　parameters,　and　an　evidence　discount　factor　is　used　to　redistribute　the　basic　probability　of　evidence　to　avoid　the　conflict　of　D-S　evidence　theory.　Finally,　the　evidence　is　fused　and　inferred　from.　The　confidence　level　of　the　insulation　state　proposition　is　obtained.　The　proposed　method　is　used　to　verify　the　measured　data　of　the　transformer,　and　the　results　show　that　the　confidence　distributed　result　of　the　insulation　state　not　only　accurately　reflects　the　oil-paper　insulation　state　of　the　transformer,　but　also　characterizes　its　deterioration　trend.　It　provides　guidance　for　the　formulation　of　power　transformer　maintenance　strategy.　©　2023　Power　System　Protection　and　Control　Press.　All　rights　reserved.