The title compounds (Sr 0.96− x Ba 0.04)Al 12− y Mg y O 19:Tb x (0< x<0.4; 0< y<0.18) are single-phase magnetoplumbite determined by X-ray powder diffraction analysis. The characteristic emission lines of 5D 3→ 7F j ( j=2, 3, 4, 5) and 5D 4→ 7F j ( j=4, 5, 6) of Tb 3+ are recorded under the VUV excitation. The intensive luminescence mainly comes from 5D 3→ 7F j transition when the concentration of Tb 3+ is low. However, when the concentration of Tb 3+ starts to increase from very low concentration, 5D 4→ 7F j transition is becoming dominant. Three broad excitation bands at 165, 193 and 233 nm have been observed. The band at 165 nm originates from the overlap between the host absorption and the charge transfer of Tb 3+–O 2−. The other two broad bands are the first spin-allowed and the spin-forbidden of 4f–5d transition, respectively. The experimental observation of the 4f–5d transition of Tb 3+ is consistent well with the theoretical expectations.