The microstructure of as-deposited and high temperature annealed Si-rich (< 20%) a-Si1-xCx:H was investigated by Raman spectroscopy, photoluminescence (PL) measurements and X-ray diffraction (XRD). The results show that Raman spectrum of Si-rich a-Si1-xCx:H is still dominated by Si-Si vibration except for the significant broadening of Si-Si TO band. The strong room temperature PL from as-deposited film can be explained by confinement of carriers in the a-Si clusters embedded in highly disordered C-rich region. When the films were annealed at 1250 degreesC in N-2 for an hour, although no crystalline Si-C diffraction signal was detected in XRD spectrum, the strong room temperature PL from annealed sample may originate from Si-C microcrystallites.