Nano-sized　Na0.5Bi2.5Nb2O9　(abbreviated　as　NBN)　powders　have　been　prepared　by　a　developed　sol-gel　method.　In　this　method,　Nb2O5　has　been　transformed　into　soluble　Nb　precursor　via　the　intermediate　compound　K3NbO4　using　coordination　chemistry　route.　The　X-ray　diffractometry　(XRD)　analyses　indicate　that　the　sol-gel　route　led　to　the　formation　of　phase-pure　bismuth　layer-structured　Na(0.5)Bi(2.5)Nn(2)O(9),　and　the　refined　crystal　parameters　were　a=0.5478　nm,　b=0.5472　nin　and　c=2.5185　nm　in　the　orthorhombic　space　group　A2(1)am.　The　transmission　electron　microscopy　(TEM)　analyses　reveal　that　the　obtained　powders　were　nanoplates　with　mean　size　of　about　50　nm,　and　the　sharp　diffraction　spots　indicate　the　formation　of　well-developed,　single-crystalline　NBN.　The　high-resolution　transmission　electron　microscopy　(HRTEM)　analyses　further　support　the　nature　of　the　single-crystalline　structure　of　the　NBN　nano-plate.　It　is　deduced　that　the　morphology　of　nanoplate　is　originated　from　the　inherent　layer-structure　of　NBN,　which　facilitates　the　growth　of　NBN　crystal　in　two　dimension　(2-D)　mode.