Abstract: The oxide of gallium was prepared by homogeneous precipitation in organic solvent. The physical structure and surface properties were characterized by XRD, NH₃-TPD, TEM and BET. The results reveal that γ-Ga₂O₃ was obtained after 500 ℃ heat treatment of the precursor of GaOOH. The lattice type of the γ-Ga₂O₃ is similar to that of γ-Al₂O₃, which belongs to cubic, cation-deficient spinel structure. The γ-Ga₂O₃ has a moderate acid center with larger amount of acid content. Most of the γ-Ga₂O₃ is two-dimensional nanoflakes with thickness of 10 nm and diameter of 100 nm. These nanoflakes are mainly distributed in one direction, and some of them form petal-shaped patterns. The experimental results showed that the conversion rate of dimethyl ether (DME) was about 24% at 270 ℃, which was close to equilibrium conversion. The texture properties of the catalyst had no significant change after the reaction and the specific surface of the catalyst was about 130 m²/g. The composite catalyst composed of the γ-Ga₂O₃ and Cu-based catalyst was used to DME steam reforming reaction in slurry bed at 270 ℃. The conversion of DME and selectivity of H₂ were as high as about 99% and 68%, respectively. The conversion of DME was over 95% after reaction time of 200 h.