The invention provides an IGZO thin film transistor and a method for improving the electrical property of the IGZO thin film transistor. The method comprises the following steps that a semiconductor structure is provided, the semiconductor structure comprises a substrate, a metal gate is formed on part of the surface of the substrate, and the metal gate and the upper surface of the substrate are respectively covered with a gate oxide layer; an IGZO film layer is manufactured to cover the gate oxide layer, the IGZO film layer is etched to form an active layer and a pixel electrode area, and a source electrode, a drain electrode and a passivation layer are formed above the IGZO film layer in sequence; after the IGZO film layer is etched to form the active layer, the surface of the IGZO film layer is treated through a plasma treatment process. The IGZO film layer is treated through oxygen plasma and UV radiation, the oxygen content of an IGZO film is improved, lattice imperfections between the IGZO film and the gate oxide layer are reduced, meanwhile, impurities and defects on the surface of the IGZO film can be removed, and device performance is improved.