Abstract: The Si-and C-co-doped SiO₂ films were prepared by dual ion beam sputtering techniqueon p-Si substrate from a SiO₂/Si+C composite target. And then they were annealed in N₂ ambience atdifferent temperature. There are two photoluminescence （PL） bands at 410nm （violet band） and 470nm（blue band） observed from the as-deposited and annealed samples. The variation tendency of the PLintensity for the two bands versus annealing temperature is different from each other, which suggestthat the two bands have different photoluminescence origins. Fourier transform infrared （FTIR） spectra,and X-ray diffraction （XRD） were used to characterize the microstructure. It is suggested that the 470nm PL band originate from the neutral oxygen vacancy defect, while the 410nm PL band mayoriginate from the defects at interface between nanocrystal Si_1-xC_x and SiO₂ matrix.