Large energy-storage density is observed in BaZrO3 (BZ)-modified 0.80Bi(0.5)Na(0.5)TiO(3)-0.20Bi(0.5)K(0.5)TiO(3) (BNBK) lead-free ferroelectric (FE) ceramics synthesized by conventional solid-state reaction. The energy-storage property of (1 - x)BNBK-xBZ has been investigated. Certain content of BZ can enhance the energy-storage property of BNBK by enhancing the breakdown strength. The largest energy-storage density W (1) = 0.73 J/cm(3) and efficiency of energy storage eta = 0.75 at E = 70 kV/cm are achieved in the 0.96BNBK-0.04BZ, which is significantly higher than that of BNT-based and lead-containing FE materials reported. Its energy-storage density exhibits the superior thermal stability with temperature range of 30-100 A degrees C. Those properties promise that the environmental friendly (1 - x)BNBK-xBZ ceramics are candidate for applications of energy-storage devices.