High-activity　barium　strontium　titanate　(BST)　nanoparticles　with　diameter　of　50nm　were　synthesized　via　sol-gel　method.　The　BST　particles　were　surface　modified　with　a　silane　coupling　agent　(KH550).　After　that,　the　BST　nanoparticles　were　then　compounded　with　poly(vinylidene　fluoride-co-chlorotrifluoroethylene)　(P(VDF-co-CTFE))　in　0-3　connecting　form.　Using　solution　casting　method,　P(VDF-co-CTFE)/BST　nanocomposite　thick　films　were　prepared　on　quartz　slides.　And　water-quenching　experiments　were　finally　performed　on　the　composite　thick　films.　XRD,　TEM,　TGA,　and　FE-SEM　were　used　to　characterize　the　BST　particles　and　the　obtained　films.　Results　indicate　that　the　interface　of　the　BST　nanoparticles　has　been　effectively　improved　by　surface　modification　with　KH550.　Compared　with　the　nanocomposite　films　with　uncoupled　BST　particles,　the　ones　with　KH550-coupled　BST　particles　possess　higher　dielectric　constant　(＞33),　larger　breakdown　electric　field　(＞270　MV/m),　and　lower　dielectric　loss.　Moreover,　the　surface　modification　is　also　helpful　to　improve　the　film　saturation　polarization　(Ps),　and　decrease　the　film　remnant　electric　polarization　(Pr),　thus　finally　enhancing　the　film　electrical　energy　density　(＞6.8　J/cm3　for　a　film　sample　with　BST　of　10vol%).　The　overall　results　indicate　that　the　surface　modification　for　polymer/ceramic　compounds　shows　great　potential　in　the　field　of　high-energy　storage　devices.