The present disclosure relates to a method of manufacturing an OLED device, an OLED device and a display panel. The method comprises: forming a first electrode layer over a substrate; forming a pixel define layer over the first electrode layer, the pixel define layer having a plurality of openings each corresponding to a light emitting region of each sub-pixel unit; performing a roughening process over a surface of the pixel define layer apart away from the first electrode layer; forming a hole injection layer covering the pixel define layer and the openings; and forming a hole transport layer, a light emitting layer, an electron transport layer and a second electrode layer in sequence over the hole injection layer at regions corresponding to the openings.