Aiming　at　the　problem　of　the　particle　swarm　algorithm　easily　into　the　local　optimum　in　the　process　of　solving　oil-paper　insulation　equivalent　circuit　model　parameters,　a　new　method　of　calculating　the　oil-paper　insulation　equivalent　circuit　parameters　was　proposed　combined　with　the　chaos　theory.　According　to　the　chaos　algorithm　characteristics　of　ergodicity　and　no　repetitiveness,　combining　the　chaos　disturbance　with　the　particle　swam　algorithm,　which　does　not　fall　into　local　optimal　solution,　oil-paper　insulation　equivalent　circuit　parameters　was　identified.　The　calculation　results　show　that　the　return　voltage　polarization　spectrum　obtained　by　improved　particle　swarm　optimization　algorithm　can　be　matched　better　with　the　return　voltage　polarization　spectrum　obtained　by　field　test.　The　oil-paper　insulation　equivalent　circuit　model　based　on　the　new　algorithm　can　reflect　the　insulation　condition　of　oil-paper　insulation　transformer　accurately,　which　laid　an　important　foundation　for　the　subsequent　diagnosising　oil-paper　insulation　aging.