A manufacturing method of an array substrate, an array substrate and a display device are provided. The manufacturing method of the array substrate comprises: forming a first conductive thin film (100) on a base substrate (1); and patterning the first conductive thin film (100), to form a pattern of a cathode (11) on a first region (11) of the base substrate (1), and form a pattern of a gate electrode (4) on a second region (12) of the base substrate (1). Complexity and process time of a fabrication process of an array substrate can be reduced, a fabrication process of an organic electroluminescent panel can be simplified, and production cost can be reduced, by forming a cathode layer of a light-emitting diode and a gate electrode layer of a thin film transistor in different regions of the base substrate at the same time by one patterning process.