Poly-crystalline In2O3-ZnGa2O4 nanocomposites were successfully synthesized by hydrothermal method with a mixed solution of In, Ga and Zn nitrates with equal mole ratio (In: Ga: Zn=1:1:1) and the ammonia was used as the precipitant. The effects of hydrothermal temperature and pH value of the mixed solution on the properties of the nanocomposites were investigated. The microstructure of the prepared In2O3-ZnGa2O4 nanocomposites was characterized by SEM and TEM, respectively. The growth mechanisms of In2O3-ZnGa2O4 nanocomposites were also preliminarily discussed in this study. Results reveal that the IGZO ceramics prepared by In2O3-ZnGa2O4 nanocomposites own a high relative density of 99.5% and low resistivity of 1.2 mΩ·cm, which can be applied to the preparation of IGZO thin film with superior performance.