Abstract: Cerium (Ce) and ytterbium (Yb) co-doped silicon oxide (SiOx: Ce, Yb) thin films were deposited by using magnetron co-sputtering technique. The down-conversion photoluminescence (PL) properties and structural evolution of the films after thermal treatments were studied. Under the excitation of a He-Cd 325 line, light emissions from the Ce3+ ions are rather weak while quite strong from the Yb3+ ions; the Yb PL intensity increases with elevating the anneal temperature, and both PL excitation and decay spectra indicate that energy transfer from Ce3+ to Yb3+ ions has taken place in the oxides. X-ray diffraction patterns show that Ce and Yb-related silicates have formed as the annealing temperature is higher than 1 000 ℃. The authors believe that the Yb PL can be enhanced greatly by forming high-luminescent Ce3+-related silicates in the oxide films, and thus increase the down-conversion efficiency.