(Na0.525K0.4425Li0.0375)(Nb0.9975Sb0.065Ta0.0375)O3 + 0.3 wt%CoO ceramics were fabricated as a functionof CuO addition by traditional solid state sintering process in order to develop excellent lead-freepiezoelectric ceramics composition. The addition of CuO in the LNKNTS composition ceramics caneffectively enhance the densification of the ceramics, resulting in the oxygen vacancies as hardeningeffect. The excellent piezoelectric properties of electromechanical coupling factor(kP) of 0.378, piezoelectricconstant(d33) of 152 pC/N were obtained from the 1.0 mol% CuO doped LNKNTS ceramics sintered at1,020℃ for 3 h.