An organic light emitting display panel and manufacturing method thereof and a display device, which can reduce the critical dimension bias of the pixel defining layer and improve the display uniformity is disclosed. The organic light emitting display panel includes a pixel defining layer, which is provided with a plurality of light emitting material filling areas, a metal layer provided on the pixel defining layer; the metal layer is provided with openings corresponding to the light emitting material filling areas respectively. The display effect of the organic light emitting display device is thereby improved.