The (K0.45Na0.55)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3 (KNLNTS) lead-free piezoelectric ceramics is synthesized by the traditional solid-state method with the sintering temperature of 1 130 ℃. The ceramic samples have good density and electric properties, with a density of 98 %, a piezoelectric constant of 308.7 pC/N, thickness vibration electromechanical coupling factor of 0.5, and dielectric loss of 0.043 at 1 kHz. Using the above-mentioned KNLNTS-based powder as the raw material, the 1-3 piezoelectric composites are prepared by the cutting and filling method, and the effect of thickness on the performance of the composites is studied. It is found that the piezoelectric constant and thickness vibration electromechanical coupling factor Kt both increase with the increase of thickness, the dielectric loss decreases with the increase of thickness, while the relative permittivity remains basically unchanged.