Highly　aligned　ZnO　nanotube　array　films　on　the　conducting　substrates　have　been　synthesized　by　a　simple　hydrothermal　method.　The　as-synthesized　ZnO　nanotubes　have　diameters　of　300-400nm　and　lengths　of　7μm　(the　aspect　ratios　of　∼20).　The　field　emission　of　ZnO　nanotube　array　films　shows　a　turn-on　field　of　about　4.6V/μm　at　a　current　density　of　1μA/cm　and　emission　current　density　up　to　about　0.22mA/cm2　at　a　bias　field　of　8.25　V/μm.　These　result　suggest　that　the　relatively　low　the　aspect　ratios　of　the　ZnO　nanotue　can　posses　strong　field　emission　characteristics.　©　2010　IEEE.