Piezoelectric PZT ceramics with high piezoelectric properties and good thermal stability are urgently desired concerning the practical application. New compositions of LiNbO₃ modified Pb(Ni_1/3Nb_2/3)O₃PbZrO₃PbTiO₃ ceramics have been prepared in this study. The effects of the introduction of the LiNbO₃ on the system were comprehensively investigated in terms of the phase structure, microstructure, electric properties, and thermal stability behavior of the ceramics. All compositions are located in the morphotropic phase boundary (MPB) region, and the ratio of the rhombohedral (R) phase increases obviously with the increase of LiNbO₃ concentration. With increasing the LiNbO₃ content, the piezoelectric properties were significantly enhanced. The sample added with 2% (in mole) LiNbO₃ shows excellent electric properties, including T_m = 185 ℃, ε_r= 5,643, k_p = 0.626, Q_m = 51, d₃₃ = 902 pC/N. More importantly, no thermal depolarization behavior was observed in the temperature range of 25–100 ℃. For PNN-PZT-x%LN ceramics, which is mainly attributed to the pinning effect resulted by the (Li'_Pb - Nb_Zr=Ti^·) defect dipoles.