Continuous synthesis process for monodispersed zirconia powders with ultrasonic wave mixing was developed. Reactant solutions were flowed through a T-tube with small diameter and then mixed in a microscale with ultrasonification. Reaction and aging were followed during the mixed solution of reactants is in plug flowing through a narrow long teflon tubing. Zr(n-OC4H9)4 in ethanol and H2O in ethanol were used as reactants. From this process monodispersed, spherical, non-agglomerated, singlet hydrated zirconia powders with 0.6 $mu extrm{m}$ average size were obtained. Geometrical standard deviation of the particle size distribution was less than 1.2 with ultrasonic mixing, and the geometrical standard deviation was not affected by the flow rate of the reactants.