Solid　state　refrigeration　technology　based　on　the　electrocaloric　effect　(ECE)　has　been　a　promising　candidate　for　replacing　vapor-compression　refrigeration.　Environmentally　friendly　lead-free　ferroelectric　materials　draw　much　attention　because　of　the　potential　of　the　ECE　from　their　large　ferroelectricity　and　plentiful　phase　structure.　To　realize　high　ECE　around　room　temperature　with　a　broad　temperature　span　(T-span),　a　typical　strategy　involves　shifting　ferroelectric-paraelectric　phase　boundaries　to　room　temperature　along　with　inevitable　relaxor　behavior.　However,　ferroelectricity　is　always　severely　deteriorated　while　lowering　the　Curie　temperature　(T-C)　to　room　temperature,　limiting　the　temperature　change　(Delta　T).　Herein,　a　novel　strategy　based　on　phase　engineering　of　the　incompletely　overlapped　phase　boundaries　with　rhombohedral-tetragonal　(R-T)　and　tetragonal-cubic　(T-C)　phase　boundaries　is　successfully　constructed　in　potassium　sodium　niobate　(KNN)-based　ceramics　to　enhance　the　ECE　for　the　first　time.　Combined　with　the　contribution　of　electric　field　behavior,　facilitated　polarization　rotation　under　electric　fields　originating　from　the　lowered　polarization　energy　barrier　and　the　strengthening　reversion　after　removing　electric　fields　are　revealed　along　with　strong　ferroelectricity.　Subsequently,　a　strongly　enhanced　ECE　is　achieved,　i.e.　Delta　T　=1.14　K　at　100　kV　cm(-1)　and　70　degrees　C　along　with　a　broad　T-span　of　34　degrees　C,　demonstrating　improved　comprehensive　ECE　and　conforming　to　the　demands　of　cooling　systems　of　electric　devices.　Meanwhile,　an　unusual　trend　is　presented　for　the　electric　field　dependence　of　the　ECE　coefficient　(Delta　T/Delta　E)　with　the　existence　of　the　critical　electric　field　(E-CE),　which　is　relevant　to　the　temperature.　This　work　proposes　an　environmentally　friendly　ECE　material　with　high　performance　for　solid-state　cooling　applications.