Provided are a method for preparing an organic light-emitting display panel, an organic light-emitting display panel, and a display device. The method comprises: forming a pixel defining layer on one side of a substrate; forming a pixel supporting layer on the side of the pixel defining layer away from the substrate, and causing the orthographic projection of the surface of the pixel supporting layer that faces the pixel defining layer on the substrate to be within the range of the orthographic projection of the side surface of the pixel supporting layer away from the pixel defining layer on the substrate; forming a light-emitting functional layer on the side of the pixel supporting layer away from the pixel defining layer; and removing the pixel supporting layer to obtain an organic light-emitting display panel.