The double-light-emitting-layer white organic electroluminescent devi ces with the structure of ITO/ m-MTDATA(10nm)/NPB(30nm)/Rubrene (0.2nm)/DOPPP (x nm )/TAz(10nm)/Alq₃(30nm)/LiF(0.5nm)/Al have been fabricated by using the method of vacuum thermal evaporation.The fluor escent dye 1-(2,5-dimethoxy-4-(1-pyrenyl)-phenyl)pyrene (DOPPP) is the blue emitting layer and the 5,6,11,2-Tetraphenylnaphthacene(Rubrene)is the yellow emitting layer.The lum inescence performances of the devices are studied by adjusting the thickness of DOPPP layer.When the thickne ss of DOPPP layer is less than 25nm,the device has yellow emission mainly.When the thickness is 25nm,t he performance of the device is the best.The maximum luminance is 9232cd/m^2when th e current density is 209.18 mA/cm²,and the maximum current efficiency is 4.68 cd/A when the current density is 103.712mA /cm².With the increasing of voltage,color coordinates change from (0.366,0.365) to(0.384,0.399).They ar e in the scope of white light.It is a better white light emission.When the thickness is more than 25nm,the e fficiency and luminance of the devices begin to reduce.