Space　charge　accumulation　is　one　of　the　major　factors　threatening　the　safe　operation　of　DC　cables.　Quantitatively　characterizing　the　trapped　charge　distribution　and　understanding　the　root　causes　of　the　traps　within　polyethylene　materials　used　in　DC　cables　are　of　great　significance　to　suppress　space　charge　accumulation　and　secure　DC　cable　operation.　Therefore,　we　charged　low-density　polyethylene　(LDPE)　and　crosslinked　polyethylene　(XLPE)　films　using　the　DC　corona　charging　method　to　simulate　the　injection　process　of　space　charges.　Taking　the　de-trapping　process　of　trapped　charges　in　polymeric　materials　into　consideration,we　proposed　a　model　based　on　isothermal　surface　potential　decay　(ISPD).　The　distribution　of　trapped　charges　was　obtained　by　analyzing　the　ISPD　data　of　the　LDPE　and　XLPE　films,　and　then　the　effects　of　morphological　characteristics　of　LDPE　and　XLPE　and　the　effects　of　additives　on　the　formation　of　traps　were　analyzed.　The　results　show　that　there　are　two　trap　centers,　i.e.　a　shallow　trap　center　and　a　deep　trap　center　for　each　film.　In　the　samples,　the　density　of　hole-type　deep　trapped　charges　is　higher　than　that　of　shallow　ones,　i.e.　the　hole-type　trapped　charges　are　mainly　deep　traps　for　both　LDPE　and　XLPE.　The　quantity　difference　between　shallow　and　deep　hole-type　charges　is　smaller　in　XLPE　and　the　density　of　shallow　trapped　hole-type　charges　in　XLPE　is　higher　than　that　in　LDPE.　The　crosslinking　byproducts　have　an　important　influence　on　the　formation　of　internal　traps　in　XLPE,　and　the　depth　of　the　traps　formed　by　additives　is　not　exactly　the　same.　©,　2015,　Science　Press.　All　right　reserved.