Environment-friendly　lead-free　piezoelectric　materials　with　excellent　piezoelectric　characteristic　and　outstanding　temperature　stability　play　an　important　role　in　advanced　functional　applications.　The　past　two　decades　have　seen　a　great　enhancement　of　piezoelectric　coefficients　(d33)　in　(K,　Na)NbO3　based　piezoceramics,　but　one　notoriously　unresolved　issue　is　their　severe　temperature　instability,　obstructing　them　toward　practical　applications.　This　work　proposes　a　novel　strategy　to　optimize　the　thermal　stability　of　KNN-based　ceramics　by　constructing　polar　topological　domains,　which　is　driven　by　the　competition　between　inhomogeneous　polarization　configuration　in　multiple　symmetry　phases　accompanied　by　the　local　oxygen　octahedral　distortion,　tilt　and　displacement.　Thanks　to　the　particular　topological　protection　of　polar　topological　domain　with　high　density　nanodomain　walls,　a　superior　temperature　reliability　(d33　decreased　only　by　10　%　in　the　temperature　range　of　25–120　°C)　was　realized,　and　the　cantilever　beam-type　piezoelectric　energy　harvester　assembled　using　the　optimized　sample　displayed　excellent　high　temperature　power　generation　capacity,　demonstrating　that　modulating　polar　topological　domains　is　an　effective　avenue　to　develop　new　high-performance　functional　material　for　practical　engineering　applications.　©　2025　Acta　Materialia　Inc.