Al₂O₃ thin films are widely applied in mechanic, optic and electronic fields due to their excellent properties. Among many deposition techniques, magnetron sputtering is regarded as one of the most practical approaches for preparing Al₂O₃ films. In sputtering process, the use of powder targets could offer the advantages of easily variable and controllable composition and low cost. However, it is not yet known well enough how to determine sputtering parameters, microstructure and properties of Al₂O₃ films from powder targets. In this work, Amorphous Al₂O₃ films were prepared by radio frequency magnetron sputtering process in which high pure Al₂O₃ powder was used as the target material. The effects and mechanism of the sputtering parameters on the microstructures, surface morphology and optical properties of amorphous Al₂O₃ films were analyzed by XRD, AFM, surface profile, UV-Vis spectroscopy and so on. Considering used as the packaging material, the antimicrobial performance of amorphous Al₂O₃ films was also studied. The experimental results showed that: increasing the oxygen flow, decreasing the sputtering power and shortening the sputtering time could make the particle size and roughness of amorphous Al₂O₃ films lower while depressing the deposition rate of amorphous Al₂O₃ films. Moreover, the increase of the oxygen flow and decrease of the sputtering time would widen the band gap which the maximum was up to 4.21 eV, and heighten the transmittance of the visible light which was beyond 90%. The antibacterial rate of amorphous Al₂O₃ films under the natural light after 24 h was up to 98.6%, which reflected the photocatalytic characteristics of the antimicrobial mechanism.