Abstract: A C/C composite as a thermal conducting material was prepared by the impregnation of unidirectional mesophase pitch-based carbon fibers with mesophase pitch and graphitization at 3 000℃. It was thinned to around 10 nm in the direction parallel to the fiber axis by cutting, grinding and ion beam bombardment. Results indicate that mesophase pitch is transformed into hexagonal graphite (HG). However, there is rhombohedral graphite (RG) tens of nanometer thick mingled with the HG. Defects include the glide and rotation structures and grain boundaries.