Abstract: The morphology, microstructure and graphitization degree of C/C composites fabricated by chemical vapor infiltration were studied by SEM, HRTEM, selected area electron diffraction and laser Raman spectroscopy. The pyrolytic carbons were rough laminar with a thickness from several 10nm to several 100nm, and were aligned parallel to the fiber axis and easily split and twinned by ion beam irradiation. A disordered zone with a thickness of about 15nm was also identified between the carbon fibers and the pyrolytic carbons, the formation of which may be dependent on the infiltration process. Both the carbon fibers and pyrolytic carbon had a low degree of graphitization and R(R=ID/IG+D’) decreased from the inner to the outer layers of the pyrolytic carbons.