Er3+, Yb3+ codoped ZrO2 nanocrystalline powders were prepared by chemical co-precipitation. We determined the crystal structures and the room temperature upconversion emission properties of samples with different doping concentrations of Yb3+ and at different sintering temperatures, respectively. It is shown that the monoclinic phase increases with the sintering temperature and the tetragonal phase increases with the increasing of Yb3+ concentration. We found that the green emission intensity and the red emission intensity of the samples sintered at 800℃ were enhanced with the increasing of Yb3+ concentration, but the red emission intensity increased much more. The quadratic dependence of the green and the red emissions on excitation power indicates that a two-photon absorption process occurs under 976nm excitation. The infrared emission properties were also discussed in the present paper.