In recent years, semiconductor devices are developing towards high heat dissipation, high breakdown field strength and low energy consumption, so the ultra-wide band semiconductor material β-Ga2 O3 has a broad application prospect. However, effective doping is the basis for realizing β-Ga2 O3 devices. In this paper, Ga2 O3 / Al / Ga2 O3 / Al / Ga2 O3 composite structure is experimentally prepared by magnetron sputtering, and the Al atoms are thermally diffused into the film by high- temperature annealing at the same time, so as to form Al-doped β-Ga2O3 thin film. Then, the laser zone melting method was used to melt and recrystallize the film area to further enhance the doping quality. The Al-doped β-Ga2O3 thin films were tested and characterized in terms of crystal properties, impurity content and optical properties. The experimental results show that: Al doping basically does not change the crystal structure of β-Ga2O3 thin films; the impurity content is gradually enhanced as the sputtering time of the Al layer becomes longer; in terms of the optical properties, the ultraviolet (UV) absorptivity of the films is 40% and 50% when the Al sputtering time is 5 and 10 s, and the UV absorption of the Al-doped β-Ga2O3 thin films is gradually enhanced with the increase of Al sputtering time; the light absorption of β-Ga2O3 thin film is close to 90% when the Al sputtering time is 300 s; and the low concentration of Al doping leads to the narrowing of the band gap width of β-Ga2O3 thin film.