Simultaneously　achieving　large　piezoelectricity　and　excellent　thermal　stability　in　a　piezoceramic　is　highly　desired　for　constructing　advanced　high-temperature　electromechanical　coupling　devices.　Here,　a　large　hightemperature　piezoelectric　coefficient　(d33　=　523　pC/N　at　200　degrees　C)　with　a　small　fluctuation　rate　(eta　＜=　+/-　10　%)　over　an　ultra-broaden　temperature　range　of　48-342　degrees　C　was　achieved　in　novel　zBiScO3-xBiInO3-yPbTiO3　(zBS-xBIyPT)　ternary　perovskite　piezoceramics　with　a　high　Curie　temperature　of　440　degrees　C.　The　morphotropic　phase　boundary　(MPB)　of　multiphase　coexistence　can　be　driven　and　optimized　in　this　system,　which　is　mainly　responsible　for　the　enhanced　piezoelectricity,　and　the　optimal　MPB　composition　is　located　at　x/y/z　=　0.010/　0.625/0.365.　The　excellent　temperature　stability　of　the　optimal　MPB　sample　should　be　attributed　to　the　increase　in　the　number　of　thermally　stable　irreversible　non-180　degrees　domains.　zBS-xBI-yPT　perovskite　ceramics　with　excellent　comprehensive　high-temperature　piezoelectric　properties　exceed　many　reported　lead-based　counterparts,　and　are　more　suitable　for　electromechanical　coupling　applications　at　harsh　elevated　temperatures.