PACS 75.30.Gw, 75.50.Vv, 76.80.+y The site occupancy and anisotropy distribution of Al substituted BaFe 12-x Al x O 19 (0.0 ≤ x ≤ 4.0) have been studied with Mössbauer spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The results suggest that the coercivity, magnetization, and magnetocrystalline anisotropies are closely related to the distributions of Al 3+ ions on the five iron sites. Mössbauer spectra indicated that Al 3+ ions have a strong preference for the 4f 1 , 2a and 12k sites. The substitution of Al 3+ by Fe 3+ in the system causes a drastic reduction of the saturation magnetization while the coercivity first increases to 8.6 kOe, for x = 2.0, and then decreases to 6.9 kOe, for x = 4.0. The origin of the changes in the magnetic properties caused by Al 3+ substitution can be attributed to the site preferences.