ZnO/Al2O3nanocomposite　tetrapods　(T-ZnO/Al2O3)　with　different　thickness　of　Al2O3film　were　fabricated　by　thermal　evaporation　ZnO　tetrapods　(T-ZnO)　followed　by　atomic　layer　deposition　(ALD)　of　Al2O3.　The　effects　of　Al2O3on　the　optical　and　field　emission　properties　of　T-ZnO　were　investigated.　The　results　show　that　the　deposition　of　Al2O3on　the　surface　of　T-ZnO　will　introduce　surface　defects　between　the　T-ZnO　and　Al2O3interfaces,　leading　to　the　decrease　of　the　turn　on　field.　However,　with　the　further　increase　of　Al2O3thickness,　the　field　emission　properties　deteriorate.　The　T-ZnO/Al2O3with　one　ALD　Al2O3cycle　exhibited　the　lowest　turn-on　field　of　1.37 V/μm　and　the　highest　field　enhancement　factor　of　6427.　The　post-annealing　treatment　will　further　improve　their　field　emission　properties　due　to　the　incorporation　of　Al　in　the　ZnO.　©　2016　Elsevier　B.V.