In order to improve the luminescence properties of the blue organic li ght-emitting diodes (OLEDs),a thin buffer layer of MgF_2is sandwiched betwee n the indium-tin-oxide (ITO) and the hole transporting layer of NPB in OLEDs.The structure is ITO/MgF₂(x nm)/NPB(50nm)/DPVBi:DSA-ph(30nm)/Alq₃(30nm)/LiF (0.6nm)/Al (100nm).By optimizing th e thickness of MgF_2buffer layer,the optimized OLED with a 1.0nm MgF_2is obtained.The expe rimental results indicate that the devices with MgF_2thin layer of 1.0nm can achieve a peak cu rrent efficiency of 5.51cd/A and the maximum luminance of 23290cd/m²( at 10.5V),which are improved by 47.3% and 25.2%,respectively,compared with the standard device without MgF_2buffer l ayer.At the same time,the results of the measurement of the surface work function of ITO show th at the buffer layer of MgF_2can modify the surface of the ITO and effectively decrease the b arrier height between ITO and NPB,improve the hole injection efficiency,which results in bet ter balanced injection of electron and hole,and more efficient exciton formation.So the perf ormance of the blue OLEDs has been improved,which makes the foundation in order to achieve high efficiency and stable full-color display and white OLEDs.