Using blue emitting material, 4-bis(2,2-diphenylvinyl)-1,1-biphenyl (DPVBi) and orange dopant 5,6,11,12,-tetraphenyl-naphthacene (Rubrene), white organic light emitting devices (WOLEDs) have been fabricated. The location of rubrene doped definite thickness 50 in the emitting layer, DPVBi influences the electroluminescence (EL) and I-V characteristics are studied. As the gap from the NPD/DPVBi interface to the doped layer is increased, the intensity of blue peak enhances rapidly and turn-on voltage becomes higher. When doped layer is contacted with NPD, electroluminescence spectrum is seriously changed by applied voltage. However, devices with the gap, although this gap is very thin 0.5nm, have good stability of color index by applied voltage.