ZrO₂ spherical nanometer powders containing 3.5 mol% Y₂O₃ have been prepared via the coupling route of water/oil (W/O) emulsion with dimethyl oxalate homogenous precipitation. ZrO₂ powders and their precursor powders have been characterized by XRD, TEM and SEM. According to the XRD result, phase volume fractions of powders were calculated by comparing the peaks’ intensities of spectrum. Furthermore, phase crystal lattice constants were obtained using crystal interplanar spacing formula and Bragg equation. With these results, the theoretical density of powders was analyzed. Finally, powders’ spherical degree was revealed via the method of comparison between theoretical density and actual density.