With high mobility, low leakage current, and good film uniformity and process compatibility, IGZO thin film transistors(TFTs) have been widely used in the field of display panels, and have also shown good application prospects in fields, such as DRAM. However, in order to realize the larger-scale application of IGZO TFTs, some problems still need to be solved, such as the reliability of the devices [2,3]. To better understand and improve the property of IGZO TFTs, we have developed a theoretical study of amorphous IGZO transistors based on the first-principles calculations to investigate the physical mechanisms that affect the mobility of IGZO thin-film transistors. Figure 1 shows the model of IGZO with crystal and amorphous structure. The fractional-wave state density plots of the amorphous model constructed and the charge density plots of the valence band top-band-tailed state and the conduction band bottom-band-tailed state are given in Fig. 2. Figure 3 illustrates the average inverse participation ratio (<IPR>), localization length (ξ) and mobility (μ) of the amorphous model with different annealing rates and different densities, respectively. In Fig. 3(a), the disorder of the amorphous system increases with increasing annealing rate, leading to an increase in the localization of the electronic states at the bottom of the conduction band. In Fig. 3(b), as the density of the system increases, the degree of localization of the electronic states at the bottom of the conduction band decreases and the mobility increases significantly. This phenomenon is related to the denser overlap of the electron cloud between ions. The inverse participation ratios and localization lengths for the oxygen vacancy defect model are given in Table 1. The results show that oxygen vacancies lead to an increase in the localization of the electronic states at the bottom of the conduction band. For deep-donor oxygen vacancies, the interaction of In ions with In ions at the vacancies forms localized defect states in the forbidden band, which affects the electron transport between InOx polyhedra and leads to an increase in the degree of electronic localization in the conduction band. For the latent donor oxygen vacancies, the defect states are eliminated during the annealing process and no localized defect states exist in the forbidden band. However, this process is accompanied by large atomic displacements, and the InOx polyhedra will move away from each other, again affecting the electron transport and leading to an increase in the degree of electron localization in the conduction band.