A preparation method of a poly-silicon thin film transistor (TFT) array substrate and an array substrate thereof are provided. The preparation method includes: forming a photoresist layer on a poly-silicon layer, and exposing and developing the photoresist layer with a gray tone mask to form patterns of a photoresist completely-reserved region, a photoresist partially-reserved regions and a photoresist completely-removed region; removing part of the poly-silicon layer located in the photoresist completely-removed region, to form patterns of active layers; ashing the photoresist so as to expose part of the active layer located in the photoresist partially-reserved regions and inject P+ ions of high concentration into the part of the active layer, to form doping regions of patterns of source-drain electrodes of a P-type TFT; and stripping off remaining photoresist.