This　paper　presented　a　large　area,　planar　backlight　unit　(BLU)　by　field　emission　technology,　which　was　different　from　edge　lighting　lamp　BLU.　The　large　area　field　emission　cathodes　of　tetrapod-like　ZnO　were　prepared　by　screen　printing　on　elaborate　Ag　electrodes.　Then　a　34-inch　planar　field　emission　ZnO　BLU　device　was　sealed　under　10-7　Torr.　The　morphologies　of　tetrapod-like　ZnO　and　cathode　were　investigated　by　scanning　electron　microscope　(SEM).　The　field　emission　performances　showed　that　ZnO　BLU　had　no　change　after　aging　treatment.　Moreover,　good　performance　of　luminance　brightness　as　4680　cd/m2　was　obtained.