An organic light-emitting diode array substrate and a manufacturing method thereof and a display device are provided. The OLED array substrate includes a base substrate, a power line and a pixel structure disposed on the base substrate. The power line is disposed under the pixel structure and is at least partially overlapped with the pixel structure; an insulating layer is disposed between the power line and the pixel structure, and a first via hole structure is disposed in the insulating layer; and the power line is connected with a driving transistor in the pixel structure through the first via hole structure.