Bismuth potassium titanate – strontium titanate (1-x)Bi0.5K0.5TiO3-(x)SrTiO3 (BKT-ST) lead-free ceramics when x = 0-0.20 were synthesized by the solid state reaction method with normal sintering. The ferroelectric phase transition was studied by X-ray diffraction (XRD). All compositions showed a single phase perovskite structure with tetragonal symmetry at room temperature and the phase structure transformed from ferroelectric tetragonal – paraelectric cubic in the range of x ³ 0.10 . Dielectric study revealed that the dielectric relaxor behavior was induced with increasing ST and transition temperature (Tm@εr max) of ST-doped BKT had a tendency to decrease with increasing ST. The Bi0.5K0.5TiO3 – SrTiO3 system was expected to be a new and promising candidate for lead-free capacitors.