Various lead-free (Kx(N)a(1-x))(0.98)Li-0.02(Nb-0.82-yTa0.18Sby)O-3 ceramics with x = 0.50, y = 0.00-0.07 or x = 0.40-0.60, y = 0.05 were prepared by the conventional solid-state reaction method. Systematic investigation on the microstructures, crystalline structures, and dielectric and piezoelectric properties was carried out. Remarkably strong piezoelectricity has been achieved in (K0.45Na0.55)(0.98)Li-0.02(Nb0.77Ta0.18Sb0.05)O-3 ceramic, which shows the excellent piezoelectric properties of d(33) = 413 pC/N, d(31) = -153 pC/N, k(p) = 0.50, and k(33) = 0.62. It is considered that the observed strong piezoelectricity should be ascribed to several combined decisive factors, such as the phase coexistence due to an orthorhombic-tetragonal polymorphic phase transition near room temperature, the high electronegativity of Sb5+ ions as compared with those of Nb5+ ions and Ta5+ ions, and the relatively ideal microstructure with high density, large average grain size and narrow grain-size distribution.