Dense and fine-grained (Na0.535K0.485)(1-x)Li-x(Nb0.8Ta0.2)O-3 (x=0.02-0.07) (abbreviated as NKLxNT) lead-free piezoceramics were fabricated by spark plasma sintering (SPS), followed by postannealing in air. All the NKLxNT ceramics showed single perovskite structures with a phase transition from an orthorhombic symmetry to a tetragonal one across a composition region of 0.04 < x < 0.05. The sample with a composition of x=0.05 had the maximum values of piezoelectric coefficient (d(33)=243 pC/N) and planar electromechanical coupling coefficient (k(p)=46.1%), and other good properties such as Q(m)=85, epsilon(r)=1240, and tg delta=0.023. Because of the enhanced densification and refined microstructure, the SPS-processed NKLxNT ceramics also had better fracture strength than that prepared by normal sintering.