Single-crystalline　KNbO3　nanocubes　with　orthorhombic　phase　were　prepared　in　a　large　scale　by　a　simple　one-step　molten　salt　route　without　using　any　surfactant　as　template;　the　nanostructures　exhibited　high　piezoelectric　properties　such　as　d(33)　=　105　pC/N　and　k(p)　=　0.34　as　piezoelectric　materials.