Embodiments of the present disclosure provide an OLED substrate and a fabrication method thereof, and a display panel. The method for fabricating an OLED substrate includes: forming an auxiliary cathode in a display region on a base substrate; forming an organic material functional layer in the display region on the base substrate where the auxiliary cathode is formed; applying a voltage to the auxiliary cathode to deform the auxiliary cathode, such that the organic material functional layer is ruptured by the deformed auxiliary cathode to form a connection channel; and forming a cathode in the display region on the base substrate where the organic material functional layer is formed. The cathode is electrically connected to the auxiliary cathode at the connection channel.