Embodiments of the present invention provide an array substrate, a manufacturing method thereof and a display device. The manufacturing method of an array substrate, comprising: forming a gate electrode on a base substrate by a first patterning process, and then depositing a gate insulating layer on the base substrate on which the gate electrode is formed; forming source and drain electrodes on the base substrate obtained after the above step, by a second patterning process; forming an active layer formed of a graphene layer, and a protective layer disposed on the active layer, on the base substrate obtained after the above steps, by a third patterning process; and forming a planarizing layer on the base substrate, obtained after the above steps, by a fourth patterning process, in which the planarizing layer is provided with a through hole through which the source or drain electrode is exposed.