The invention discloses an array substrate and a manufacturing method thereof and a display device, relates to the field of display, and can solve the bad display problems of greenish phenomenon, horizontal X-talk and the like of a liquid crystal display and improve the image quality of the display device, in particular a high-resolution product on the premise of not reducing the transmittance rate. The array substrate comprises a substrate, a semiconductor layer, source and drain electrode layers, a grid insulation layer, a first grid metal layer, a second grid insulation layer and a second grid metal layer, wherein the semiconductor layer, the source and drain electrode layers and the grid insulation layer are arranged on the substrate in sequence from bottom up; the first grid metal layer is arranged on the grid insulation layer; the second grid insulation layer is arranged below the semiconductor layer; and the second grid metal layer is arranged between the second grid insulation layer and the substrate.