Highly efficient phosphorescent white organic light-emitting diodes (WOLEDs) with stable emission spectra are successfully fabricated by using an RGB three-color separately monochromatic emission layer (EML) structure.The EML consists of a sequence of bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate) iridium (lⅢ)(Ir(MDQ)2(acac)) doped tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as the red emission layer,iridium,tris(2-phenylpyidine)(Ir(ppy)3) doped TCTA as the green emission layer and iridium(Ⅲ) [bis(4,6-difuorophenyl)pyridinato-N,C2]picolinate (Flrpic) doped a mixed-host of TCTA and tris(4-carbazoyl-9-ylphenyl)amine (26DCzPPy) as the blue emission layer.Without using any out-coupling techniques,the resulting WOLEDs achieve a power efficiency of 42lm/W at 100cd/m2,and 34lm/W at 1000cd/m2.The WOLEDs also show excellent spectrum stability with bias voltages,remaining the Commission Inteationale de L Eclairage coordinates at (0.44,0.43) from 1000 cd/m2 to 10000 cd/m2 and the color rendering index is as high as over 80.We contribute the stable emission spectrum to the RGB separate EML structure that successfully suppresses the undesired competition between host-guest energy transfer and direct exciton formation on emissive dopants by effectively controlling the position of exciton recombination region.