Abstract: In order to determine the proper heat t reatment temperature for C/ C composites with different fibrevolume f ractions, C/ C composites were made by needled felt with fibre volume f raction of 40 %, 30 % and 25 % densifying through three times of CVI. The graphitization degree of C/ C composites without heat t reatment and withheat t reatment at 2200 ℃and 2400 ℃was investigated by means of X-ray diff raction and Raman spectra. The resultsshow that the microst ructures of three kinds of C/ C composites are smooth laminar (SL), and C/ C composites withhigher fibre volume f raction have higher graphitization degree ; the st ress graphitization takes place at the interfacebetween fibre and smooth laminar pyrolytic carbon and different smooth laminar pyrolytic carbons and the former islarger than the later, which is the reason why C/ C composites with higher fiber volume f raction have higher graphi2tization degree. The higher the heat t reatment temperature ( HTT), the higher the st ress graphitization degree.