The invention relates to a thin-film-transistor array substrate and a forming method thereof. The array substrate comprises an insulating base, a first metal layer, a grid insulting layer, a noncrystalline silicon layer, a first conducting transparent material layer, a doped noncrystalline silicon layer, a second metal layer, a passivated layer and a second conducting transparent material layer, wherein the first metal layer is positioned above the insulating base, and a first part of the first metal layer forms a TFT grid which is electrically connected with a scanning line; the grid insulating layer is covered above the first metal layer and the insulating base; the noncrystalline silicon layer and the first conducting transparent material layer are both positioned above the grid insulating layer; the doped noncrystalline silicon layer is positioned above the noncrystalline silicon layer and forms a TFT semiconductor layer together with the noncrystalline silicon layer; the second metal layer is positioned above the doped noncrystalline silicon layer and the first conducting transparent material layer, a first part of the second metal layer forms a source electrode and a drain electrode of the TFT, and the source electrode is electrically connected with a data wire; the passivated layer is positioned above the second metal layer and is used as an insulator; the second conducting transparent material layer is positioned above the passivated layer, and a first part of the second conducting transparent material layer forms a pixel electrode connected with the drain electrode; and the first conducting transparent material layer forms part of a common electrode.