Designing　high　temperature　piezoelectric　ceramics　with　large　electromechanical　properties　is　key　to　the　actuators　application　in　harsh　environment.　BiFeO3-BaTiO3　based　piezoelectric　ceramics　are　the　promising　candidates　due　to　their　high　electromechanical　properties　and　high　Curie　temperature.　Here,　the　simple　A-site　single　K+　doped　0.63Bi1−xKxFeO3-0.37BaTiO3　(abbreviated　as　0.63B1−xKxF-0.37BT)　ceramics　with　positive　temperature　dependent　electromechanical　properties　were　fabricated　via　conventional　solid　phase　method.　The　electromechanical　properties　in　the　0.63B1−xKxF-0.37BT　ceramics　are　closely　related　to　the　content　of　K+　doping.　The　excellent　electromechanical　properties　of　S=　0.26%　and　d33*=861　pm/V　under　low　electric　field　of　30　kV/cm　at　105　are　achieved　in　the　0.63B0.9975K0.0025F-0.37BT　ceramic,　which　is　conducive　to　their　application　at　high　temperature.　Combined　with　the　microstructure　and　PFM,　the　optimized　electromechanical　properties　in　0.63B0.9975K0.0025F-0.37BT　ceramic　are　mainly　due　to　more　nanodomains　switching　facilitated　by　the　large　grain　size　and　local　structural　heterogeneity.　The　site　engineering　of　A-site　single　ion　doping　is　an　efficient　and　simple　strategy　for　BF-BT　based　piezoelectric　ceramics　to　achieving　excellent　electromechanical　properties　under　low　electric　field　at　high　temperature.　©　2021　Elsevier　B.V.