A TFT device of a liquid crystal display and a manufacturing method therefor are provided. The TFT device has: a substrate; a first metal layer formed on the substrate on which a first silicon nitride protective film is deposited; a second metal layer deposited on the first silicon nitride protective film on which a second silicon nitride protective film is deposited; and a conductive film deposited on the second metal layer where the second silicon nitride protective film is etched, and connected with the first metal layer through a contact hole which passes through the first and second silicon nitride protective films, so that the first and second metal layers are connected. Thus, the connecting distance of the conductive film between the different metal layers and the contact resistance between metals are decreased, so as to enhance the product yield rate and the competitive capability of the product.