A series of SnO₂ thin films doped with low-dose Al (≤1mol%) were prepared on slide glass substrates by radio frequency (RF) magnetron sputtering. The crystal structure and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-IR spectrometer, and photoluminescence (PL) measurements. Results show that the lattice constant c decreases with increasing the Al content, which implies that Al atoms are successfully introduced into the SnO₂ and occupy the Sn sites, and large number of oxygen vacancies are generated. The average transmittance values are higher than 88% within the visible spectral region (400~800 nm) for all the films. The bandgap broadens when the Al percentage increases, which is dominated by the Burstein-Moss (BM) effect. The PL spectra of these films have near band edge and deep level emission under the radiation excitation of 265 nm wavelength. The observed intensity of these peaks increases consistently with increasing the Al percentage.