Biaxially　oriented　polypropylene　(BOPP)　film　used　in　pulse　film　capacitors　withstands　high　temperatures　for　a　long　time.　This　leads　to　frequent　faults　in　pulse　film　capacitors,　affecting　the　reliability　of　the　pulse　system.　In　this　paper,　the　thermal　aging　tests　of　BOPP　films　at　100°C　for　10–80　days　are　carried　out　in　this　paper,　and　the　physicochemical　and　electrical　properties　of　the　aging　materials　are　characterized.　The　results　show　that　more　deep　and　shallow　traps　to　BOPP　films　are　introduced　during　the　thermal　aging　process.　With　the　increase　in　aging　time,　the　breakdown　field　strength　gradually　decreases,　and　the　conductivity　decreases　first　and　then　increases.　Under　the　action　of　thermal　aging　for　a　long　time,　the　recrystallization　of　materials　and　the　destruction　of　molecular　chains　by　thermal　aging　are　the　main　reasons　for　the　increase　of　traps　and　the　decrease　of　breakdown　field　strength.　The　former　is　dominant　in　the　early　stage　of　aging,　and　the　latter　is　dominant　in　the　late　stage　of　aging.　Therefore,　the　conductivity　shows　the　law　of　slow　decrease　first　and　then　rapid　increase.　The　relevant　research　provides　a　theoretical　foundation　for　the　process　improvement　and　life　prediction　of　BOPP　films.　©　2024　Wiley　Periodicals　LLC.