Trivalent erbium ions doped zirconia nanocrystal was prepared by co-precipitation method. X-ray diffraction analysis was used to determine the crystal structure. The grain sizes were calculated to be about 10 nanometers by Scherrer's equation. Raman spectra showed that the phonon energy of the host was low. Under the excitation by a 980nm laser diode
the sample presented a strong green emission as well as a weak red emission of up-coversion luminescence.