Nanoparticle scattering layer based on polymer-metal oxide composite is successfully introduced to enhance the light extraction efficiency of organic light emitting diodes (OLEDs). We find that the density and the distribution of nanoparticles is the key factor to maximize the light extraction efficiency of pristine OLEDs by out-coupling the unusable light with the scattering film. In our experiment, 71 wt% of Al(2)O(3) mixed with polymer matrix shows the increase of light extraction efficiency of 40%. This method is expected to play a critical role to create the low-power OLED application such as OLED lightings with simple fabrication process and low cost.