Abstract: Three carbon/carbon composites with rough laminar, smooth laminar and dual matrix carbon were prepared by chemical vapor infiltration(CVI) using hydrogen-diluted methane, CVI using nitrogen-diluted propane, and two-step CVI using first methane/hydrogen and carbon dioxideand then furan resin impregnation and carbonization. The influence of the microstructure of the carbon matrix on the internal friction behavior of the composites was investigated. Results indicate that the microstructure of the carbon matrix plays an important role in the internal friction. The overall internal friction is related to the motion of dislocations, the sliding of the fiber/matrix interface and the sliding of the carbon planes. The internal friction of the composite is very sensitive to temperature and amplitude, but less sensitive to frequency. Among these composites, the dual matrix carbon has the highest density of crystal-defects and the highest internal friction while the rough laminar carbon has perfect carbon planes and the lowest internal friction.