The present invention provides methods for manufacturing a thin film transistor (TFT) array substrate and a display panel. The method for manufacturing the TFT array substrate comprises the following steps: forming a plurality of gate electrodes, a gate insulating layer, a semiconductor layer, an ohmic contact layer, an electrode layer and a photo-resist layer on a transparent substrate in sequence; using a multi tone mask to pattern the photo-resist layer; forming a plurality of source electrodes and a plurality of drain electrodes at both sides of the channels, respectively; heating the photo-resist layer; etching the semiconductor layer; removing the photo-resist layer; forming a passivation layer on the channels, the source electrodes and the drain electrodes; and forming a pixel electrode layer on the passivation layer. The present invention can reduce an amount of the required masks in the fabrication process, and only one wet etching is required to etch the metal material on the TFT array substrate.