The present application relates to the field of display technology and, in particular, to an array substrate, a manufacturing method of the array substrate, and a display device. An array substrate comprises: a base substrate having a pixel display area and a gate drive circuit area; a first thin film transistor formed in the pixel display area, the first thin film transistor comprising a first gate insulating layer; a second thin film transistor formed in the gate drive circuit area, the second thin film transistor comprising a second gate insulating layer, where a thickness of the second gate insulating layer is smaller than a thickness of the first gate insulating layer.