Aiming　at　the　return　voltage　polarization　spectrum　with　local　peaks　which　failed　to　clearly　diagnosis　transformer　insulation　condition,　based　on　the　time　domain　dielectric　response　theory,　combined　with　the　recovery　voltage　measurement　data,　the　extended　Debye　model　was　introduced　into　the　equivalent　circuit　of　dielectric　response,　and　the　system　equivalent　circuit　of　transformer　oil　paper　insulation　model　was　established.　The　relationship　between　the　return　voltage　polarization　speculation　and　dielectric　response　equivalent　model＇s　parameters　was　established　by　simulating　and　analyzing　the　non-standard　polarization　spectrum.　Simulation　results　show　that　changing　of　each　branch＇s　parameters　produces　local　peaks　of　the　polarization　spectrum,　moreover　the　front　of　the　polarization　spectrum＇s　local　peaks　reflect　the　condition　of　the　transformer　insulating　oil.　Simultaneously　the　experimental　study　result　demonstrates　that　the　simulation＇s　conclusion　is　effective　and　indicates　that　the　non-standard　polarization　spectrum　can　be　used　to　diagnose　the　insulation　condition　of　transformers.