Yttria-stabilized zirconia (Zr0.92Y00.08O 2-5 :YSZ) thin films have prepared on AI2O3 substrates by RF magnetron sputtering. The as-deposited YSZ thin films prepared at 500 °C exhibits the (020) peak at 2θ-34.8°, which corresponds to the peak position of the YSZ single crystal. The Zr4n, Y3 and valence-band states were confirmed by photoemission spectroscopy (PES). The YSZ thin film at wet air exhibits higher conductivity and lower activation energy than that at dry air. The obtained PES spectra demonstrate the O-H bond and Fermi level shift of the YSZ thin film at wet air are observed by PES spectra. These results indicate that the YSZ thin film exhibits proton conduction at wet air in the intermediate temperature (IMT) region of 300~500 °C.