Increasing　power　density　and　excess　heat　production　in　integrated　electronic　devices　create　the　strong　demand　for　polymeric　thermal　management　materials　with　excellent　thermal　stability,　flame　retardancy　and　thermal　conductivity.　To　this　end,　high-performance　ionic　liquid-wrapped　boron　nitride　nanosheets　(BNNS@IL)　were　firstly　simultaneously　exfoliated　and　flame-retardant　functionalized　via　one-step　ball　milling　process　based　on　the　strong　mechanochemical　action.　Epoxy　(EP)-based　layered　films　with　highly　in-plane　oriented　BNNS@IL　were　then　fabricated　by　a　novel,　effective　and　solvent-free　cyclic　layer-by-layer　(CLbL)　blade-casting　method.　Arising　from　the　highly　flat　oriented　structure　and　rich　flame-retardant　functional　groups　of　BNNS@IL,　as　well　as　the　high　compatibility　between　filler　and　matrix,　the　as-fabricated　EP/BNNS@IL　films　exhibited　high　anisotropic　thermal　conductivity　(K-parallel　to　of　8.3　and　K-perpendicular　to　of　0.8　W　m(-1)　K-1),　outstanding　thermal　stability　and　flame　retardancy　with　a　dramatic　decrease　in　PHRR　(104.2　W/g)　and　THR　(8.1　kJ/g)　corresponding　to　reductions　of　72.9%　and　75.7%　compared　with　neat　EP,　respectively.　Additionally,　the　flat　oriented　structure　and　strong　interfacial　interaction　also　endow　EP/BNNS@IL　films　with　high　flexibility　and　excellent　mechanical　properties.　Therefore,　the　high-effective　CLbL　casting　method　and　the　obtained　high-performance　EP-based　film　exhibit　a　significant　potential　application　in　high　power　flexible　electrical　devices　and　thermal　management　products.