Phosphor-converted　white　light-emitting　diodes　(LEDs)　are　currently　playing　key　roles　in　the　lighting　and　display　industries　and　trigger　urgent　demands　for　the　discovery　of　＂good＂　phosphors　with　high　quantum　efficiency,　improved　thermal　stability,　and　controllable　excitation/emission　properties.　Herein,　a　general　and　efficient　heterovalent　substitution　strategy　is　demonstrated　in　K2HfSi3O9:Eu2+　achieved　by　Ln(3+)　(Ln　=　Gd,　Tb,　Dy,　Tm,　Yb,　and　Lu)　doping　to　optimize　luminescence　properties,　and　as　an　example,　the　Lu3+　substitution　leads　to　improvement　of　emission　intensity　and　thermal　stability,　as　well　as　tunable　emission　color　from　blue　to　cyan.　The　structural　stability　and　Eu2+　occupation　via　Lu3+　doping　have　been　revealed　by　the　structural　elaboration　and　density　functional　theory　calculations,　respectively.　It　is　shown　that　heterovalent　substitution　allows　predictive　control　of　site　preference　of　luminescent　centers　and　therefore　provides　a　new　method　to　optimize　the　solid-state　phosphors　for　LEDs.