AlN　skeleton　structure-reinforced　highly　oriented　graphite　flake　(AlN/GF)　composites　have　become　a　promising　candidate　for　thermal　management　materials　owing　to　their　high　thermal　conductivity　and　low　thermal　expansion.　However,　the　applications　of　AlN/GF　composites　are　still　limited　by　their　poor　mechanical　properties.　Herein,　a　carbon　nanotube-coated　alumina　(Al2O3@CNT)　hybrid　was　used　as　a　reinforcement　to　improve　the　mechanical　performance　of　AlN/GF　composites　prepared　via　vacuum　infiltration　followed　by　spark　plasma　sintering.　It　was　found　that　the　relative　density　and　orientation　degree　of　the　composites　decreased　slightly　with　an　increase　in　the　Al2O3@CNT　content　from　0　to　2　wt%.　However,　the　fracture　toughness　and　bending　strength　of　the　composites　improved　significantly　after　the　introduction　of　the　Al2O3@CNT　hybrid　reaching　up　to　1.66　MPam1/2　and　95　MPa,　respectively,　which　correspond　to　an　improvement　of　approximately　50%　and　20%　over　those　of　the　AlN/GF　composite.　With　the　addition　of　the　Al2O3@CNTs,　the　thermal　expansion　of　the　composites　increased　from　7.3　×　10-6/K　to　∼15.5　×　10-6/K,　while　the　thermal　conductivity　decreased　from　442　to　∼253　W/m/K.　The　toughening　and　strengthening　mechanisms　as　well　as　the　thermal　impact　mechanism　of　the　composites　were　also　investigated.　©　2021　Elsevier　Ltd　and　Techna　Group　S.r.l.