An array substrate, a manufacturing method thereof and a display device are provided. The manufacturing method includes: forming a light-shielding pattern layer, a buffer layer, an active layer, a gate insulating layer and a gate electrode on a base substrate, which are away from the base substrate in sequence; depositing an amorphous silicon (a-Si) film on the base substrate in a temperature range of 15-150° C.; forming a first interlayer dielectric (ILD) at least disposed above the active layer by patterning the a-Si film; forming through holes in the first ILD, through which a source contact region and a drain contact region of the active layer are exposed; and forming a source electrode and a drain electrode on the first ILD, which are respectively connected with the source contact region and the drain contact region via the through holes.