Provided are an OLED display panel and its manufacturing method, as well as a display device. The OLED display panel includes: a base substrate; and an organic light emitting unit, a pixel defining layer and a packaging substrate, arranged on the base substrate. The pixel defining layer is provided with a via hole at least one side of the organic light emitting unit. The via hole is filled with a total reflection-eliminating layer through which incident light is processed to obtain emergent light capable of arriving at an interface between the packaging substrate and an atmosphere at an incident angle smaller than a total reflection angle at the interface between the packaging substrate and the atmosphere.