Abstract: Top-emitting white organic light-emitting device was fabricated by optimizing the thickness of MoOx layer with high refractive index and low absorption in the visible region, which is used as out-coupling layer. The structure of the device is Si/Ag(60nm)/MoOx(2nm)/NPB(50nm)/DPVBi(7nm)/rubrene(0.2nm)/Alq3(43nm)/LiF(1nm)/Al(1nm)/Ag(20nm)/MoOx (xnm). We analyzed the influence of out-coupling layers growth on devicesperformance. We researched the influence of the MoOxs thicknesses on EL spectrum. With the increase of MoOx thickness, the transmittance was enhanced for blue light region and the spectrum covered visible light region. CIE was changed from (0.30, 0.49) to (0.33, 0.42) when we added 30nm MoOx as out-coupling layer. When the outcoupling layer was 40nm MoOx, CIE was (0.30, 0.38). It is found that the CIE moved to the equal energy point.