We report a multi-layer white organic light-emitting device (WOLED) bas ed on emissive layer,in which Ir(ppy)_3and Ir(piq)₂(acac) are codoped into BPhen h ost,and the fluorescent blue material DPVBi is employed in the WOLED.The efficient WOLED is obtai ned by varying the thickness of the doped layer.The maximum luminance and electrolumine scense (EL) efficiency of the device with the doped layer thickness of 25nm are 8489cd/m^2and 4.55cd/A,respecti vely.The Commission Internationale De L′Eclairage (CIE) coordinates of the device vary f rom (0.52,0.34) at 4V to (0.34,0.26) at 12V,which are generally within the white region.The perform ance of WOLED may be tuned by changing the thickness of doped layer,and the simple device structures and excellent reproducibility make it well suitable for low-cost lighting applications an d ben eficial to the industrialization.