A series of strontium barium niobate-based B2O3 system glass–ceramics have been prepared by conventional melting and heat-treated crystallization method. The effect of BaF2 addition in nucleation and crystallization kinetics has been explored for dielectric applications. BaF2 addition decreased the activation energy of crystallization obviously and changed microstructure of glass–ceramics significantly. The dielectric constant and breakdown strength of glass–ceramics were improved significantly by adding BaF2. The glass–ceramic with a relative dielectric constant of 337 and a breakdown strength of 52.7 kV/mm was achieved.