The disclosure provides a thin film transistor (TFT) and a fabrication method thereof, an array substrate and a fabrication method thereof, and a display apparatus. The fabrication method of a TFT includes: forming a protection layer in an area on an active layer between a source electrode and a drain electrode to be formed, forming a source-drain metal layer above the active layer having the protection layer formed thereon, coating a photoresist on the source-drain metal layer, and forming a photoresist reserved area corresponding to areas of the source electrode and the drain electrode to be formed and a photoresist non-reserved area corresponding to the other area; etching off the source-drain metal layer corresponding to the photoresist non-reserved area to form the source and drain electrodes and expose the protection layer above the active layer; and removing the photoresist above the source and drain electrodes and the protection layer.