Hexagonal　boron　nitride　nanosheet　(h-BN)　is　widely　applied　to　polymer-based　nanocomposites　due　to　its　good　thermal　and　insulation　properties.　Moreover,　surface　modification　can　contribute　to　improving　dispersity　and　compatibility　of　nanofillers　in　polymer-based　nanocomposites.　Epoxy　resin　(EP)　nanocomposites　filled　with　functionalized　h-BN　can　further　improve　its　thermal　and　insulating　properties.　In　this　work,　a　novel　surface　modification　method　of　grafting　dopamine　(DA)　at　the　end　of　3-glycidoxypropyl-trimethoxysilane　(KH560)　is　proposed　to　modify　h-BN　(DKB)　as　well　as　DKB　and　its　corresponding　EP　nanocomposites　are　prepared　successfully.　The　dispersibility　of　EP　composites　filled　with　h-BN　is　firstly　discussed.　Besides,　the　thermal　performance　and　breakdown　field　strength　of　EP　nanocomposites　filled　with　modified　h-BN　are　mainly　investigated.　The　results　show　that　surface　modification　method　of　DKB　can　effectively　enhance　the　dispersity　and　compatibility　of　h-BN　in　the　EP　polymer.　The　thermal　stability　and　thermal　conductivity　of　DKB/EP　nanocomposites　has　significant　improvement.　Meanwhile,　breakdown　field　strength　of　DKB/EP　nanocomposites　is　also　superior　to　that　of　other　h-BN/EP　nanocomposites.　©　2021　IEEE.