Based　on　the　eigenvalue　measurements　of　return　voltage,　the　fruit　flying　algorithm　is　adopted　to　calculate　the　equivalent　circuit　parameters　of　transformer　oil-paper　insulation,　which　are　then　applied　in　the　simulation　model　to　obtain　the　polarization　spectrum　of　return　voltage.　It　fits　the　measurements　very　well,　verifying　the　correctness　of　calculated　parameters.　Seven　transformers　are　divided　into　three　groups　according　to　their　voltage　level　and　capacity,　their　equivalent　circuit　parameters　of　oil-paper　insulation　are　calculated　and　the　effect　of　insulation　condition　on　the　parameters　is　analyzed.　The　analytical　results　show　that,　the　transformer　with　better　insulation　has　bigger　insulation　resistance,　polarization　resistance　and　maximum　time　constant.　©,　2015,　Electric　Power　Automation　Equipment　Press.　All　right　reserved.