(Bi0.5Na0.5)TiO3-BaTiO3　lead-free　piezoelectric　ceramics　exhibit　excellent　piezoelectric　properties,　but　its　piezoelectric　property　with　high　thermal　stability　is　the　major　obstacle　limiting　the　potential　application.　In　this　study,　the　KNbO3　(KN)　was　adopted　to　0.875((Bi0.5Na0.5)TiO3-0.125BaTiO(3)　(BNT-12.5BT)　by　conventional　solid-state　reaction　to　enhance　the　piezoelectric　properties　in　high　temperature.　The　results　of　X-ray　diffraction　(XRD)　indicate　that　KN　has　diffused　into　BNT-12.5BT　lattices　to　form　a　pure　perovskite　structure　and　not　exert　a　severe　disturbance　on　the　ferroelectric　tetragonal　lattice.　The　depolarization　temperature　T-d　is　maintained　at　a　high　level.　For　piezoelectric　properties,　at　KN　modification　x　=　0.01,　the　piezoelectric　coefficient　(d(33))　increases　to　147　pC/N　from　135　pC/N　for　unmodified　composition.　Meanwhile,　the　d(33)　will　increase　to　187　pC/N　until　the　depolarization　temperature　(185　degrees　C)　arrives,　showing　the　excellent　temperature　stability　of　the　piezoelectric　properties　to　meet　the　actual　demand.