A series of IGZO thin films were deposited using magnetron sputtering with different condition (substrate temperature, sputtering time, sputtering power, O2 flow rate, anneal temperature), and were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), nano-beam electron diffraction (NBED) and energy dispersive spectrometer (EDS). The technological parameters and methods of preparing crystalline IGZO were studied. The results show that the thickness of the IGZO film has a significant effect on the crystallization of IGZO. When the thickness of the IGZO film is above 3000 ?, the crystallization effect is obvious, and is not affected by the film forming temperature, power and other factors. The crystallization of IGZO can be promoted effectively by 600℃ annealing treatment after the film formation is completed, but the effect of film formation temperature and O₂/Ar ratio on the crystallization of IGZO is not obvious. The crystalline IGZO active layer can be effectively prepared by adjusting the film thickness and annealing temperature. By optimizing the film forming conditions of IGZO, the back-channel etching structure IGZO TFT (thin film transistor) with mobility of 29.6 cm²/(V·s) was prepared, which was about three times higher than that of amorphous IGZO TFT, and the electrical characteristics of IGZO TFT were significantly improved.