In this experiment, new high-temperature piezoelectric ceramics (1−x)K0.45Na0.55NbO3−x(Bi0.5Li0.5)0.9Sr0.1ZrO3 were prepared by the conventional solid-state sintering method, and the effect of the doping amount of (Bi0.5Li0.5)0.9Sr0.1ZrO3 on the microstructure and electrical properties of this system ceramics were systematically investigated. XRD, SEM, EDS, and other modern test technology analysis results show that all the doped ions have entered the KNN lattice in the studied range, forming a dense solid solution with a pure perovskite structure, and forming orthorhombic–tetragonal polymorphic phase boundaries at 0.02 ≤ x ≤ 0.035, the ceramics exhibit rhombohedral–tetragonal polymorphic phase coexistence in the range of 0.04 ≤ x ≤ 0.05. The electrical properties tests show that the ceramics of this system exhibit excellent electrical properties in the multiphase coexistence region at x = 0.04, which are: d33 = 307pC/N, kp = 46%, εr = 1363, tanδ = 2.79%, Pr = 16.7 µC/cm2, Ec = 12.65 kV/cm, and TC = 368 °C. These excellent electrical properties and the high Curie temperature predict that the ceramics of this system have great prospects for future applications in the field of lead-free piezoelectric ceramics.