Potassium tantalite (KTaO3) nanocrystalline with octahedral morphologies were synthesized by hydrothermal route. The as-prepared samples have pyrochlore structures, which are consisted of a large quantity of octahedral nanocrystalline with a uniform edge size of about 500 nm. The band gap energy for KTaO3 nanocrystalline is about 4.06 eV. The Raman studies show that the vibration modes of nanocrystalline are red-shifted and broadened, which are due to defects of KTaO3 nanocrystalline and weak quantum confinement effect. PL study exhibits that a broad blue light emission band peaking at about 490 nm (2.53 eV) was observed at room temperature. Oxygen vacancies should be accounted for this emission peak. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.