The microstructures and dielectric properties of barium strontium titanate glass-ceramics are closely related to the AlF3 and MnO2 additions. The grain morphology was changed by adding AlF3, while the dielectric loss was decreased significantly by adding MnO2. At the same time the breakdown strength (BDS) was improved by doping 4 mol% AlF3 and 1 mol% MnO2 with the glass-ceramics. The present investigation resulted in the development of glass-ceramic compositions with high dielectric BDS and low dielectric loss for high energy density capacitor applications.