The present invention discloses an array substrate, a preparation method therefor, an optical touch screen and a display device, to solve problems in the prior art that the preparation process of built-in optical touch screens is complex and high in cost. The array substrate comprises a plurality of first sensing wires that are formed at a gate metal layer and that extend along a row direction; a plurality of first photosensitive elements and a plurality of second photosensitive elements that are formed at a semiconductor layer and that are insulated from each other; a plurality of second sensing wires that are formed at a source drain metal layer and that extend in a column direction; and a blocking electrode formed on the gate metal layer, wherein the blocking electrode is located below the second photosensitive members. The first photosensitive elements located in a same row are electrically connected with a same first sensing wire; the second photosensitive elements located in a same column are electrically connected with a same second sensing wire; the first photosensitive elements and the second photosensitive elements are used to generate a current signal according to external light; and the first sensing wires and the second sensing wires are used to transmit current signals produced by the first photosensitive elements and current signals produced by the second photosensitive elements respectively.