Metasurface is an artificial nanostructured, planar type metamaterial that be able to manipulate light through tailoring the localized coupling between electromagnetic wave and nano-scale antennas. Here, we propose a new OLED architecture (MOLED) that combines a phase-controllable, reflective metasurface to the micro-cavity OLEDs in order to overcome technical limits of existing OLEDs (pixel scaling limit or low power efficiency). In the metasurface embedded Fabry-Perot cavity, the resonance wavelength is mainly determined by adjusting the reflection phase of metasurface, not by a cavity length. It allows MOLED to implement ultra-high density RGB pixels (> 10,000 PPI) without using FMMs (fine-metal-mask) or color filters. It also demonstrates twice the luminance efficiency and superior color purity (bandwidth <35nm), compared to the color-filtered white-OLED method.