Field　emission　properties　of　zinc　oxide　(ZnO)　nanoparticles　(NPs)　decorated　carbon　nanotubes　(CNTs)　are　investigated　experimentally　and　theoretically.　CNTs　are　in　situ　decorated　with　ZnO　NPs　during　the　growth　process　by　chemical　vapor　deposition　using　a　carbon　source　from　the　iron　phthalocyanine　pyrolysis.　The　experimental　field　emission　test　shows　that　the　ZnO　NP　decoration　significantly　improves　the　emission　current　from　50　mu　A　to　275　mu　A　at　550　V　and　the　reduced　threshold　voltage　from　450　V　to　350　V.　The　field　emission　mechanism　of　ZnO　NPs　on　CNTs　is　theoretically　studied　by　the　density　functional　theory　(DFT)　combined　with　the　Penn-Plummer　method.　The　ZnO　NPs　reconstruct　the　ZnO-CNT　structure　and　pull　down　the　surface　barrier　of　the　entire　emitter　system　to　0.49　eV　so　as　to　reduce　the　threshold　electric　field.　The　simulation　results　suggest　that　the　presence　of　ZnO　NPs　would　increase　the　LDOS　near　the　Fermi　level　and　increase　the　emission　current.　The　calculation　results　are　consistent　with　the　experiment　results.