Germanium nanocrystals embedded in SiO 2 glassy matrix have been prepared on glass substrates and Si(100) wafers by r.f. cosputtering and post annealing methods. Raman scattering spectra at various annealing temperature were measured. Compared with bulk Ge, a red shift and broadening of Raman scattering spectra were observed. According to the parameters of Raman scattering spectra, we calculated the average crystal size of nc Ge. The experimental results are in agreement with the phonon confinement theory.