Improving　the　space　charge　accumulation　of　epoxy　resin　insulation　can　improve　the　reliability　of　HVDC　power　devices.　This　work　investigates　the　surface　modification　of　hexagonal　boron　nitride　(h-BN)　by　silane　coupling　agent,　which　could　improve　thermal　conduction　while　restraining　space　charges　of　epoxy　resin.　Surface　modified　BN　(KBN)　was　produced　by　the　hydrolysis　reaction　method.　The　epoxy/BN　nanocomposites　with　different　nanoparticle　contents　were　produced　using　suitable　dispersing　and　curing　techniques.　FTIR　and　SEM　were　used　to　characterize　the　chemical　grafting　and　dispersity　of　the　nanocomposites.　The　measured　space　charge　behavior　was　then　analyzed　and　discussed.　The　results　show　that　the　silane-oxygen　groups　appear　on　the　BN　surfaces　after　modification,　increasing　the　chemical　compatibility　between　BN　and　epoxy　resin　matrix.　Incorporation　of　1%　by　weight　of　KBN　makes　it　possible　to　effectively　suppress　space　charge　accumulation　at　20　kV/mm.　Whereas　for　high　content　samples　(10　wt%),　a　small　amount　of　positive　charge　accumulations　can　be　observed　near　the　anode.　The　introduction　of　shallower　traps　responds　to　the　positive　charge　accumulations.　Given　the　deep　trapping　at　the　interface,　the　height　of　the　injection　barrier　is　increased　in　the　low　grade　samples.　Future　work　should　be　focused　on　the　interface　states　near　the　electrodes.　©　2022　IEEE.