This paper presents an investigation of heterogeneity of the degree of graphitization for a carbon cloth reinforced carbon matrix composite material, which has a low crystalline extent. First, the fiber and the matrix carbon with different micro structures in the composite are analyzed respectively by using the micro Raman spectroscopy. To further study this heterogeneity of the degree of graphitization, the carbon fiber and the matrix carbon are prepared separately under the same processing with the composite, and are characterized by X-ray diffraction and peak separation, respectively. The experiment results indicate that the composite can be decomposed into three constituents with large difference of degree of graphitization. The results are in accordance with the microstructure analysis under the polarized light illumination and micro Raman spectroscopy analysis. The causes leading to a low degree of graphitization of the composite are pointed out, and the key steps to manufacture composite with high degree of graphitization are emphasized. (C) 2003 Elsevier B.V All rights reserved.