Abstract: The development of high-performance potassium sodium niobate (KNN)-based piezoelectric ceramics to replace lead-based ceramics is vital for sustainable social development. However, the piezoelectric constant (d₃₃) of KNN-based ceramics exhibits strong temperature dependence. In this study, through doping MgTiO₃ into K_0.44Na_0.52Li_0.04Nb_0.80Ta_0.20O₃ ceramics, a “doping-phase boundary engineering-lattice modulation” tripartite synergistic strategy was employed to simultaneously improve both d₃₃ and temperature stability. High-performance KNN-based lead-free piezoelectric ceramics were successfully prepared by solid-state reaction method. The effects of the introduction of MgTiO₃ on the microstructure, piezoelectric properties and temperature stability of the ceramics were systematically investigated. Among them, the KNLNT-0.02MT ceramic sample exhibited excellent piezoelectric properties (d₃₃ = 256 pC/N, d₃₃* = 478 pm/V, S_max = 0.1423%). Compared to the undoped sample, the d₃₃ and d₃₃* increased by 30.6% and 54.7%, respectively, while exhibiting excellent temperature stability (the d₃₃ values were reduced of only 12.1% over the temperature range of 25 to 250 ℃). This work provides valuable insights into the design of high-performance, wide-temperature-range lead-free piezoelectric ceramics.