Gallium oxide (Ga₂O₃) is an important wide bandgap transparent conductive oxide with many excellent properties, which is widely used in many fields such as catalysis, electroluminescence, biology, and so on. This review mainly introduces the researches on the preparation, properties and applications of gallium oxide nanomaterials. Initially, the preparation of gallium oxide by hydrothermal method has been highlighted and the effects of hydrothermal conditions on the morphologies and sizes of the final products were summarized. Furthermore, the unique properties of gallium oxide in the fields of electricity, gas, heat, and biomedicine are introduced, and the excellent luminescent properties of gallium oxide are emphasized. Additionally, this review mainly introduces the applications of gallium oxide in the fields of catalysis, gas sensors, optoelectronic devices, high voltage electronic devices and biomedicine. Finally, the problems and shortcomings in current research on gallium oxide nanomaterials are discussed and the opinions and prospects are put forward for the future perspective of the research in gallium oxide nanomaterials.