The present disclosure provides an OLED display motherboard and a method for manufacturing the same, a method for manufacturing the OLED display panel, and an OLED display device thereof. The OLED display motherboard includes a base substrate having a display region and a non-display region surrounding the display region, a TFT and an OLED device located within the display region of the base substrate, at least two crack stop slits located within the non-display region of the base substrate, an extending direction of the crack stop slit being the same as an extending direction of an edge of the display region of the base substrate, and adjacent crack stop slits being separated by a crack stop slit step, and an encapsulation layer covering the crack stop slit and the OLED device. A portion of the encapsulation layer has a non-uniform thickness.