Nano　dielectrics　have　brought　hope　for　solving　the　problem　of　cable　insulation　at　high　voltage　levels.　In　this　paper,　nano　Al2O3　and　MgO　are　doped　to　silicone　rubber　and　the　nanocomposites　are　aged　at　200　degrees　C　for　0-80　days.　The　electrical　conductivity　and　DC　breakdown　characteristics　of　aged　materials　are　investigated.　The　microscopic　and　elemental　properties　are　also　analysis.　It　is　found　that　with　the　increase　of　thermal　aging　time,　electrical　conductivity　of　all　sets　decreases　first　and　then　increases,　while　the　DC　breakdown　voltage　experiences　a　process　of　first　increasing　and　then　decreasing.　During　the　initial　aging　process,　secondary　vulcanization　of　silicone　rubber　occurs,　however,　the　cross-linked　network　degrades　with　further　aging,　which　could　explain　the　changes　in　electrical　properties.　The　introduction　of　metal　oxides　could　react　with　exfoliated　radicals　to　form　s　table　compounds,　thus,　the　performance　of　Al2O3　and　MgO　doped　materials　have　better　electrical　properties　under　thermal　aging.　(C)　2022　Published　by　Elsevier　Ltd.