The present invention discloses an array substrate and a method for preparing the same, and a display device. The array substrate comprises a substrate, and a thin-film transistor and a passivation layer formed on a side of the substrate, and the array substrate is divided into a reflective region and a transmissive region, wherein an insulating layer is formed on the reflective region on a side of the passivation layer that is far from the substrate, and a nanoparticle layer for diffuse reflecting an incident light is formed on a side of the insulating layer that is far from the substrate. Not only the viewing angle of the array substrate is enlarged, but also the performances of the array substrate such as transmittance, contrast and dark-state uniformity are guaranteed, thus the present invention is especially applicable for display devices for large-scale outdoor display.