Lead-free piezoelectric ceramics with formula (Li0.12Na0.88) (Nb1-x%Sbx%)O-3 were prepared by the conventional solid-state reaction method. The effects of Sb5+ doped into (Li0.12Na0.88) NbO3 B site were studied. Within the selected compositional range, all the samples have a single perovskite structure. The crystal structure changed from rhombohedral to orthorhombic at x=1, and from orthorhombic to tetragonal symmetry at x=6. The presence of orthorhombic to tetragonal morphotropic phase boundary was proposed when 3 < x < 6. By substituting Sb5+ for Nb5+, dielectric property and impedance characteristic were enhanced, but the Curie temperature and the ferroelectricity were decreased. The optimum composition was x=3, for which the maximum value of the mechanical quality factor Q(m) was as high as 1780, piezoelectric constant d(33) and Curie temperature T-c were 45 pC/N and 300 degrees C, respectively.