The present disclosure relates to an OLED display substrate including a base substrate, a thin film transistor array layer and a planarization layer on the base substrate, and an anode, a pixel definition layer, a cathode, and a light emitting layer on a side of the planarization layer away from the base substrate, the pixel definition layer defining pixel regions, the light emitting layer being located on a side of the pixel definition layer away from the base substrate. The display substrate further includes a light guide that is in contact with the light emitting layer and is used to lead out light from the light emitting layer, so as to test the led-out light and adjust light emission.