Abstract: A variety of synthesis parameters for the preparation of Zirconia nanoparticles in watercylcohexanehexanolTriton X100 microemulsion have been investigated. The results show that reaction temperatures and the molar ratio of water to surfactant(r0) were the predominant factors to control the specific surface area as well as particle sizes of ZrO2 . The particle size first decreased with a decrease in the value of r0, then increased after reaching a critical particle size upon further decreasing the r0 value; on the other hand, an increase in the reaction temperature led to smaller ZrO2 particles, but the ZrO2 particle size became larger at a temperature close to the cloud point of the reverse micelles, where a small temperature disturbance would easily lead the system out of the microemulsion phase. XRD, TEM and N2 adsorption experiments were used to characterize the ZrO2 sample. XRD results showed that the fresh sample was amorphous, and tetra nal phase appeared as a predominant phase with a little monoclinic modification upon calcining the sample at 450 ℃, further heating the sample at 900 ℃ would lead to more monoclinic modification in intensity, but tetra nal phase was still predominant. TEM showed that the average particle size was increased from about 4 nm at 450 ℃ to about 21 nm at 900 ℃, which was in agreement with the measurements from N2 adsorption results and XRD results. N2 adsorption experiments indicated that a specific surface area of 212 m2•g－1 was obtained after optimizing the synthesis parameters and calcining the obtained sample at 450 ℃ in oxygen.