The commercial success of Erbium-doped Optical Fiber Amplifier (EDFA) is stimulating the development of Erbium-doped Waveguide Amplifier (EDWA) which is expected to play a key component in the long-distance optical communication system in the future due to its compacted volume and low power consuming. Er ions can emit strong light at 1.55 μm that coincides with the optical communication wavelength. Therefore, when Er³⁺ ions are doped in a compacted waveguide structure, these ions can be excited by pump light to emit near 1.55 μm and thus amplify the signal light. Numerous studies have shown that, the fluorescence performance of Er³⁺ is closely related to the factors like matrix material, doping method, preparation and annealing conditions. Especially, many available Er³⁺-doped matrix materials have been studied so far, some of which show good properties in achieving compacted and high-gain waveguides. Among them, Er doped Al₂O₃ waveguide has been demonstrated to have excellent performance in optical amplification. Ga is located at the same group of Al, and thus gallium oxide (Ga₂O₃) has similar physical and chemical properties of Al₂O₃. Meanwhile, Ga₂O₃ has many unique advantages, such as high Er³⁺ doping, broad half width of full maximum in photoluminescent peak at 1.55 μm and high refractive index. Therefore, Ga₂O₃ has the potential to be used as a host material to fabricate planar optical waveguide device for optical amplification, however, there are no such reports in the literature. In this paper, the fabrication and properties of the erbium-doped gallium oxide films are reported. The films are characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The effect of the Er-doping concentration, thermal annealing temperature and film thickness on the photoluminescence properties are studied. The results show that the films are amorphous even at an annealing temperature up to 600 ℃. The maximum photoluminescence intensity appears in the film prepared at 40 W erbium oxide sputtering power and 600 ℃ annealing temperature. After optimizing the film performance, we start structural design of the Ga₂O₃ waveguide. Considering the fact that the fluorine-based gas reacts with Ga₂O₃ to form volatile gas and non-volatile GaF_x is easily adhered to the surface of the film that is difficult to be removed, fluorine-based plasma is not effective in etching Ga₂O₃. On the other hand, direct etching of the materials containing metallic rare earth element usually leads to the aggregation of the residual metallic Er due to the different etching rate between the host materials and Er. Both could result in a very rough etched surface in the waveguide. In order to solve this problem, two kinds of waveguide structures, e.g., erbium-doped Ga₂O₃ film filled into SiO₂ channel and erbium-doped Ga₂O₃ film coated on the top of the SiO₂ ridge waveguide, are designed to avoid the issues caused by direct etching of Er-doped Ga₂O₃ film. The light field distribution in these two types of waveguides are simulated in order to maximize the interaction between the light and the effective Er-doped area. Then the waveguides are prepared based on the structural parameters from the simulation, the silicon wafer with a 2 μm thick thermally oxidized layer is used to prepare SiO₂ channel and ridge structures via lithographing and etching by Ar/CHF₃ etching gas, and then Er-doped Ga₂O₃ film with a thickness of about 400~500 nm is deposited on these structures to get the final waveguide structure. The minimum propagation loss at 1 310 nm is 1.26 dB/cm. In the future, it is expected to optimize the processing conditions of thin films and waveguides and reduce the optical loss, which could provide the possibility for the preparation of erbium-doped waveguide amplifier with better performance.