A new lead-free piezoelectric system of (1 - x) (K0.48Na0.52+y)(Nb0.95Sb0.05)O-3-x(Bi0.8La0.2)(0.5)(Na0.8Li0.2)(0.5) ZrO3 [(1 - x)KNayNS-xBLNLZ] were prepared using the conventional solid-state sintering method. The effects of BLNLZ content and Na excess on the microstructure and electrical properties of the ceramics were investigated. It was found that an enhanced dielectric, ferroelectric, and piezoelectric behavior has been attained by successfully constructing the rhombohedral-tetragonal phase boundary in the ceramics with x = 0.04. The small Na excess can greatly improve ceramics properties due to the increase of abnormal grain growth caused by the formation of a small amount of liquid phase. As a result, the ceramic with x = 0.04 and y = 0.004 has optimum electrical properties of d(33) similar to 470 pC/N, k(p) similar to 50 %, 2P(r) similar to 32.3 mu C/cm(2), and 2E(c) similar to 14.2 kV/cm, together with a Curie temperature of similar to 210 degrees C. The giant d(33) of this ceramic system could be comparable with the most of the reported results about the alkali niobate-based lead-free piezoceramics. It was believed that such an excellent piezoelectricity of this material system will promote the development of KNN-based lead-free ceramics.