A　comparative　study　of　biaxial-orientated　polypropylene　(BOPP)　films　extracted　from　one　failed　HVDC　filter　capacitor　(serving　for　10　years)　and　one　fresh　capacitor　(spare　capacitor　from　the　same　batch)　is　reported　in　this　paper.　Experimental　results　show　that　the　10-year　online　operation　does　not　bring　about　molecular　changes;　however,　molecule　reorganization　and　recrystallization　was　detected　using　differential　scanning　calorimetry　and　dynamic　mechanical　analysis　tests.　Electrical　measurements　including　dielectric　spectra,　DC　conductivity　measurement,　DC　breakdown　strength　and　were　also　performed.　The　experimental　results　show　that　the　aging　process　causes　an　increase　in　dielectric　constant,　dissipation　factor,　DC　conductivity,　and　the　DC　breakdown　strength.　Thermal　stimulated　current　measurements　indicate　that　traps　were　introduced　by　aging　and　are　responsible　for　such　abnormal　changes.　The　nano-cavitivies　generated　by　molecule　reorganization　could　possibly　act　as　charge　traps.　Therefore,　homo-charges　can　accumulate　in　the　vicinity　of　the　electrodes,　leading　to　the　degradation　of　long-term　withstand　strength　but　an　enhancement　of　short-term　breakdown　strength.