Blue host material 9,10-di-(2-naphthyl)anthracene(ADN)was doped with Aluminum(Ⅲ)bis(2-methyl-8-quinolinato)4-phenylphenolato(BAl_q3),and the concentration of BAl_q3 was changed,then structure of ITO/NPB/ADN∶BAl_q3/Al_q3/Mg∶Ag were fabricated in the vacuum. The impact of energy-match and BAl_q3 dopant concentration on the carrier injection,transport,recombination and the color purity of the devices were analyzed. The experiment results show that BAl_q3 dopant influence the current density,luminance,efficiency and color purity of the devices. When the BAl_q3 dopant concentration is about 25%,the luminous efficiency is 1.0 lm/W,the spectrum at 440 nm,the CIE chromaticity(0.18,0.15),and the half life of unseal device is about 950 hours,which achieve both the high efficiency and good color purity.