Natural　ester　as　an　environmentally　friendly　dielectric　liquid　is　becoming　commonly　used　in　power　transformer.　However,　it　is　susceptible　to　oxidation.　Under　severe　oxidation,　the　oil　sample　could　gel　whose　impact　on　insulation　performance　is　not　known.　In　this　research,　we　focus　on　the　impact　of　the　gelling　process　of　natural　ester　on　its　breakdown　characteristics.　In　order　to　survey　this,　a　breakdown　test　platform　was　first　assembled.　Then　the　experiment　was　conducted,　with　the　results　showing　that　the　gelling　procedure　includes　three　stages,　the　liquid,　the　sol　and　the　gel.　The　sol　was　found　to　show　a　poor　breakdown　performance　and　also　impact　the　breakdown　performance　of　the　fresh　oil　if　it　is　dissolved.　The　gel,　more　in　a　solid　form　similar　to　jelly,　showed　slightly　a　higher　breakdown　performance　itself　but　slightly　impacted　the　fresh　oil　under　mixture.