Aluminum nitride (AlN) films are fabricated on well polished K9 glass substrate by reactive radio frequency (RF) magnetron sputtering technique. Influence of deposition pressure on microstructure and properties of AlN films is investigated, as other deposition parameters are kept as constants. Experiments as well as simulation are carried out to investigate microstructures and optical properties of the films in terms of deposition pressure. The results indicate that the AlN films are crystalline and the deposition pressure influences orientation of the crystallites. The films are transparent according to the transmittance spectra. The refractive index, obtained by simulation of the transmittance spectra using envelope method, and the deposition rate of the films decreases with increasing deposition pressure. The mechanism of effects of deposition pressure on structure and optical properties of AlN films is tentatively analyzed.