An array substrate, a manufacturing method thereof and a display device are provided. In the manufacturing method, the needed patterns can be formed by just three photolithography processes, wherein the semiconductor layer and the etch stop layer are formed by just one photolithography process. The method reduces one photolithography process compared to the method of the state of the art, which forms the pattern of the semiconductor layer and the etch stop layer by two photolithography processes respectively, thereby greatly reducing the manufacturing cost and improving the production efficiency.