The　time　domain　dielectric　response　diagnosis　technology　is　an　effective　nondestructive　testing　method　for　diagnosing　transformer　oil-paper　insulation　states.　The　dielectric　response　mathematical　model　of　insulation　is　a　crucial　means　of　the　time　domain　diagnosis.　To　accurately　reflect　the　medium　depolarization　process,　to　determine　the　number　of　the　relaxation　which　depolarization　process　contains,　and　to　accurately　identify　the　parameters　for　the　model,　according　to　the　research　results　of　dielectric　physics,　the　radical　exponential　decay　law　was　introduced　into　dielectric　response　function　in　order　to　make　the　function　closer　to　the　experimental　rule　in　a　variety　of　different　conditions.　At　the　same　time,　a　differential　depolarization　current　method　is　put　forward　in　the　modeling,　solving　a　controversial　problem　of　the　number　of　relaxation,　and　realizing　the　solving　of　dielectric　response　function.　The　results　show　that　the　differential　depolarization　current　method　is　accurate,　providing　a　new　idea　for　the　time　domain　dielectric　response　diagnosis　of　insulation　medium.