Nano-sized ZrO2 powders were synthesized by hydrothermal method using ZrOC12 · 8H2O and NH3 · H2O as hydrotheraml precursor raw materials and （K2O3

KOH）water/mineralizer solutions as hydrothermalme- dium;PEG as dispersant. The phase constitution

agglomerationand and physical properties of ZrO2 powders were tested by the X-ray diffraction （XRD）

Scanning electron microscope （SEM）. The effects of PH value

hydrothermal reaction temperature and concentration of mineralizers and dispersant on the agglomeration of nano-sized ZrO2 pow- ders were investigated and some solutions were suggested accordingly. The result shows： well dispersed powder par- ticle size of about 20nm nano ZrO2 powder can be prepared by the solution which PH value of 9

the hydrothermal reaction temperature is 230 ℃

dispersing agent （PEG） content of 1.5%

mineralizer （K2O3

KOH） ratio KK2O3/KOH is 3： 1.