Abstract: The ZrO₂ nano-powders were prepared from zirconium(Ⅳ) nitrate by the hydrothermal method at 180℃ for 18 h in reaction solution with different pH.The ZrO₂ powders were characterized by XRD and TEM.The ZrO₂ powders of a mixture of m-ZrO₂ and t-ZrO₂ can be directly synthesized from zirconium(Ⅳ) nitrate by the low hydrothermal process in reaction solution with different pH. When the reaction solution was added with glycerin, it was found that ZrO₂ powders with pure tetragonal phase could be directly synthesized at 180℃ with certain pH.The proportion of glycerin and the pH value of reaction solution were interrelated to the crystallographic forms of the zirconia powders.The ZrO₂ powders with pure tetragonal phase are formed at 180℃ for 18 h when glycerin was added to the reaction solution with the ratio ［glycerin］∶［ Zr⁴⁺］ greater than 1∶1 and the pH 9—11, in other experiments mixtures of monoclinic and tetragonal phase ZrO₂ were formed. The ZrO2 powders with pure tetragonal phase were about 10nm and homogenous in size. Compared with the similar experiments without glycerin, addition of glycerin was important in synthesizing the tetragonal phase-ZrO₂ powders by the low temperature hydrothermal method.