Cable　accessory　has　the　interface　formed　by　cross-linked　polyethylene　(XLPE)/silicone　rubber　(SiR),　which　is　prone　to　surface　discharge　and　thus　causes　the　failure　of　cable　system.　This　article　conducts　the　simulated　experiment　of　thermal–mechanical　aging　on　the　interface　of　XLPE/SiR.　The　interfacial　breakdown　and　dielectric　properties　under　different　aging　states　are　analyzed.　It　is　found　the　interfacial　aging　process　of　XLPE　can　be　divided　into　the　recrystallization　stage　and　the　oxidation　reaction　stage.　The　former　contributes　to　the　interfacial　roughness　and　thus　the　better　insulating　performance,　whereas　the　latter　leads　to　degradation　of　interface,　and　thus　the　worse　insulating　performance.　In　addition,　combined　with　the　established　electric　field　model　for　the　interface,　the　differences　between　thermal–mechanical　aging　and　individual　thermal　aging　on　the　interface　are　discussed.　The　sample　under　thermal–mechanical　aging　reaches　the　maximum　interfacial　breakdown　voltage　later　than　that　under　individual　thermal　aging,　but　their　performance　tends　to　be　consistent　in　the　later　stage　of　aging.　©　2023　Wiley　Periodicals　LLC.