The invention provides an array substrate and a preparation method thereof, and belongs to the technical field of display. By means of the array substrate, the problem can be solved that as the feature of an existing thin film transistor is influenced by the light of an organic light emitting diode, reverse display of a black screen is caused. The array substrate comprises a substrate, the substrate is divided into multiple subpixels in different colors, each subpixel comprises a driving region, a capacitance region and a light emitting region, and at least one thin film transistor is arrangedin each driving region; organic light emitting diodes are arranged in each light emitting region, a first color film structure corresponding to the color of the subpixel where each light emitting region is located is arranged below the organic light emitting diodes, a second color film structure is arranged below the thin film transistors, and the second color film structure and the first color film structure in at least one color are arranged in the same layer.