The present disclosure provides an OLED array substrate comprising a plurality of pixel units each including a plurality of sub-pixel units, each of the sub-pixel units comprising a light-emitting portion, each light-emitting portion having a first electrode, a second electrode and an organic light-emitting layer sandwiched between the first electrode and the second electrode, wherein the sub-pixel unit further comprises an organic film layer and a semi-reflecting mirror layer disposed successively on a light exit side of the second electrode, the first electrode comprises a reflective layer, the second electrode is a transparent electrode, a structure between the first electrode and the semi-reflecting mirror layer constitutes a microcavity structure, and organic film layers of the sub-pixel units of different colors of each pixel unit have different thicknesses. The present disclosure further provides an OLED display panel, an OLED display device, and a method of manufacturing the array substrate.