A fabricating method of a TFT array substrate includes following steps: providing a substrate having a pixel region and a bonding pad region surrounding the pixel region; forming a patterned polysilicon layer within the pixel region on the substrate; forming a first patterned insulating layer to cover the patterned polysilicon layer; forming a first patterned transparent conductive layer on the first patterned insulating layer; forming a first metal layer on the first patterned transparent conductive layer; forming a second patterned insulating layer to cover the first metal layer; forming a second patterned transparent conductive layer on the second patterned insulating layer; forming a second metal layer on the second patterned transparent conductive layer; forming a third patterned insulating layer to cover the second metal layer; and forming a third patterned transparent conductive layer on the third patterned insulating layer.