(1-x)(0.85Bi(0.5)Na(0.5)TiO(3)-0.11Ba(0.5)K(0.5)TiO(3)-0.04BaTiO(3))- xK(0.5)Na(0.5)NbO(3) lead-free piezoelectric ceramics with x=0.00, 0.02, 0.03, 0.04, 0.05, and 0.10 were prepared by a conventional solid state method. A coexistence of rhombohedral (R) and tetragonal (T) phases was found in the system, which tended to evolve into pseudocubic symmetry when x increases. The x=0.04 sample exhibited improved electrical properties: the dielectric constant epsilon(r)=1900 with the low loss tangents 0.06, the S-max/E-max of similar to 400 and similar to 460pm/V under unipolar and bipolar electric field, respectively. Meanwhile, piezoelectric constant d(33) still maintained similar to 160pC/N. These could be owed to the formation of polar nanoregions for relaxor phase.