Embodiments of the present invention disclose an array substrate and a manufacturing method thereof. The method comprises forming a patterned active layer on a gate insulating layer, the active layer covering a part of the gate insulating layer; forming a source/drain electrode material layer on the active layer and the gate insulating layer; forming a patterned insulating layer on the source/drain electrode material layer; conducting an etching process by using the insulating layer as a mask, so as to etch the source/drain electrode material layer to form a source electrode and a drain electrode, etch a part of the insulating layer to form a via hole in the insulating layer over the drain electrode, and etch a part of the active layer between the source electrode and the drain electrode to form a channel.