Disclosed are a method for manufacturing an array substrate, an array substrate and a display device. The method includes the following operations: sequentially forming a gate, a gate insulation layer, an active layer, an ohmic contact layer and a metal layer on a base substrate; forming a photolithography mask on the metal layer, a thickness of the photolithography mask being between 1.7 μm and 1.8 μm; exposing the photolithography mask through a mask plate to make a uniformity of the photolithography mask in a half-exposed area of the mask plate reach a preset uniformity; and manufacturing the array substrate based on the exposed photolithography mask.