An OLED display substrate, a touch display panel and a display device are provided. The OLED display substrate has a base substrate and a display region, the display region includes: a plurality of first sub-regions arranged at intervals and second sub-regions located between the first sub-regions; at least one OLED light-emitting unit located in the first sub-regions; a plurality of optical sensing units located in the second sub-regions, and first drive electrode lines and first transmission electrode lines connected with the optical sensing units and intersecting with each other; wherein, the optical sensing unit includes a photosensitive sensor, and the photosensitive sensor is configured to generate an electric signal according to a light intensity change of a sensed touch point; and the first drive electrode line and the first transmission electrode line are configured to provide the electric signal to determine a position of the touch point.