We have designed a new structure blue emission device with doped Alq_3 of 3% in hole transmission layers of NPB. The CIE coordination of the devices is (0.17,0.19). The maximum electroluminescence efficiency is 4.1 cd/A at 11V, the brightness is 118.8 cd/m~2 at 7 V, and the maximum brightness is 10770 cd/m~2 at 13V.