A　convenient,　simplistic　and　large-scale　molten　salt　synthetic　methodology　was　developed　to　synthesize　the　morphology-controlled　nanostructures　such　as　cube-shaped　and　rod-shaped　KNbO3.　This　method　synthesized　products　from　a　reaction　of　K2CO3　and　Nb2O5　with　the　molten-salt　medium.　The　powder　X-ray　diffraction　and　transmission　electron　microscopy　were　used　to　investigate　the　structure　and　morphology　of　the　products.　The　formation　mechanism　of　KNbO3　with　controlled　morphologies　was　analyzed.　Firstly,　the　K2CO3　diffused　onto　the　Nb2O5　surfaces　to　form　K2O-shell　in　the　molten　salts,　followed　by　the　nucleation　and　growth　of　KNbO3.　The　rod-like　structures　of　KNbO3　were　originated　from　the　directed　aggregation　of　nanoparticles　by　the　electrostatic　interactions.　However,　in　high　temperature　environment,　the　rod　shaped　KNbO3　had　the　chance　to　break　up　into　several　fragments　from　the　grain　boundaries,　resulting　in　the　individual　submicron-scale　cubes　in　the　molten　salt.