The invention discloses a thin-film transistor, a manufacturing method thereof, an array substrate and a display device. The method includes the steps that a grid graph, a gate insulation layer thin film, an active layer thin film, an ohmic contact layer thin film, a first etching blocking module and a source drain metal layer thin film are sequentially formed on a substrate base plate, wherein the first etching blocking module and the source drain metal layer thin film are located in a channel region to be formed; the first etching blocking module shields the active layer thin film and the ohmic contact layer thin film corresponding to the channel region to be formed, and the graph containing source and drain is formed through wet etching; the graph containing an ohmic contact layer and an active layer is formed through a dry etching technology. According to the thin-film transistor, the manufacturing method thereof, the array substrate and the display device, on the basis that the first etching blocking module can protect the active layer thin film corresponding to the channel region to be formed, etching of the source metal layer and the drain metal layer is completed just through a wet etching technology, etching is even, and the problems that when the dry etching technology is adopted to etch the source metal layer and the drain metal layer, etching is uneven, the equipment loss is large, and the yield is low are solved.