Nanometer-sized zirconia (ZrO₂) powder was synthesized from ZrOCl₂·8H₂O through a hydrothermal method. The aqueous suspension stability of ZrO₂ powder was studied by zeta potential measurement and particle size analysis. Results show that ZrO₂ nanoparticles are ellipsoidal with uniform particle size, and the particle size is mainly in the range of 40–100 nm. The isoelectric point (IEP) occurs at pH=9.0. ZrO₂ particles are well dispersed far from IEP and severely agglomerated near IEP.