Erbium, Ytterbium-codoped ZrO 2 nanoparticles(ZrO 2∶Er 3+ ,Yb 3+ ) were prepared by the sol-emulsion-gel technique. The purpose of the present study is the application of upconversion phosphor in the biological label. In order to make out the mechanism of upconversion under 980 nm excitation the 488 nm pump was used. The influence of temperature on the crystallite phase was studied. The results confirm the upconverted mechanism in ZrO 2∶Er 3+ ,Yb 3+ nanocrystals is due to an energy transfer upconversion(ETU). Erbium, Ytterbium-codoped ZrO2 nanoparticles (ZrO2: Er3 +, Yb3 +) were prepared by the sol-emulsion-gel technique. The purpose of the present study is the application of upconversion phosphor in the biological label. In order The make-up of the mechanism of upconversion under 980 nm excitation the 488 nm pump was used. The influence of temperature on the crystallite phase was studied. The results confirm the upconverted mechanism in ZrO 2: Er 3+, Yb 3+ nanocrystals is due to an energy transfer upconversion (ETU).