Field　emission　cathode　arrays　of　planar-gate-type　triodes　are　fabricated　on　the　glass　substrate　by　magnetron　sputtering,　conventional　photolithography　and　chemical　wet　etching.　The　carbon　nanotube　(CNT)　emitters　were　deposited　on　the　cathode　by　electrophoretic　deposition.　The　cathode　plate　and　anode　plate　were　packaged　into　a　51-cm　monochrome　field　emission　display　(FED)　with　planar-gate-type　triode,　which　is　applied　for　49-cm　liquid　crystal　display　(LCD)　as　backlight　unit　and　its　field　emission　characteristics　are　investigated.　The　field　emission　performance　shows　that　the　maximum　current　density　is　approximately　81.3　μA/cm2,　its　highest　lightness　could　reach　to　7000　cd/m2　and　luminescent　uniformity　was　more　than　96%　when　the　gate　and　anode　voltages　are　290　V　and　3　500　V,　respectively.　Moreover,　the　emission　current　fluctuation　is　less　than　6%　for　7　h.　Its　highest　lightness　for　back　light　unit　in　20-in.　LCD　could　come　to　205　cd/m2.