New lead-free piezoelectric ceramics (K0.48,Na0.52) (Nb(1-x)Sbx)O3 −0.05Ca0.2(Bi0.5,Na0.5) 0.8ZrO3 (KNNSx-CBNZ) were fabricated by traditional solid-state sintering process. The effects of Sb content on phase structures and electrical properties of the KNNSx-CBNZ ceramics were studied. Because Sb5+ can increase the rhombohedral-orthorhombic phase transition temperature and decrease orthorhombic-tetragonal phase transition temperature simultaneously, it is found that the ceramics in the composition range of 0.02<x<0.04 possess a rhombohedral-tetragonal phase boundary. The best piezoelectric properties are obtained in the ceramics with x=0.03: d33=470 pC/N, kp=52.4%, εr=1563, tan δ=3.30% and Tc=243°C. The results show that KNNSx-CBNZ ceramics have potential applications for substituting the lead based piezoelectric ceramics.