The invention relates to an array substrate and a preparation method thereof. A data reading device and an optical sensor are formed through a gate layer, a gate insulating layer, a semiconductor layer, a first conductive layer, a first protective layer, a light shielding layer, a first color barrier layer, a second protective layer and a second conductive layer. External light can be colorized bythe first color barrier layer, and then, colored image information is acquired. Thus, a sensed image has color, and the effect of image display and the user experience are improved. In addition, thefirst color barrier layer can be used to track and detect light of a specific color, judge the stability of the specific light source and enhance the light source. The first protective layer can protect the coverage area from pollution and damage. The second protective layer can prevent external extrusion damage to each layer and increase the service life, prevent the phenomenon of relative dislocation of the layers and enhance the user experience.