In　the　research　of　time-division　dielectric　response　for　oil-paper　transformer　insulation　aging　diagnosis,　there　always　exists　uncertainty　in　the　solution　spectrum　of　the　dielectric　response　spectra,　the　parameter　calculation　process　is　complex,　and　it　is　difficult　to　describe　the　physical　meaning　of　the　indirect　extracted　feature　quantity.　In　accordance　with　the　problem　in　the　circuit　model　determination　and　the　feature　extraction,　we　propose　a　new　method　to　diagnose　the　aging　condition　for　transformer　oil-paper　insulation.　Firstly,　a　terminal　two-point　analytical　method　of　depolarization　current　spectrum　is　put　forward　to　determine　the　insulation　equivalent　circuit　for　transformer　oil-paper　insulation,　a　new　type　of　polarization　maximum　straight　spectrum　is　drawn,　and　three　new　characteristic　parameters,　such　as,　the　number　of　polarization　low　resistances　lLow_R,　the　maximum　slope　of　polarization　aτmax,　and　the　maximum　intercept　of　polarization　bτmax,　are　directly　extracted.　It　is　confirmed　that,　the　more　serious　the　aging　of　oil-paper　insulation　is,　the　larger　the　number　of　lLow_R　will　be,　and　the　greater　value　of　aτmax　and　bτmax　will　be.　The　analysis　and　calculation　of　experimental　data　of　several　transformers　prove　that　the　aging　status　for　transformer　oil-paper　insulation　can　be　effectively　diagnosed　through　new　characteristic　parameters.　The　new　method　and　characteristic　quantity　of　equivalent　circuit　provide　a　new　way　to　diagnose　the　aging　of　oil-paper　insulation.　©　2019,　High　Voltage　Engineering　Editorial　Department　of　CEPRI.　All　right　reserved.