A fractal characterization approach was proposed to research pore microstructure evolution in car- bon/carbon (C/C) composites during the chemical vapor infiltration process. The data obtained from mercury porosimetry determinations were analyzed using the sponge fractal model and the thermo- dynamics relation fractal model, respectively. The fractal dimensions of C/C composites at different densification stages were evaluated. The pore microstructure evolution with densification time was studied by fractal dimension analysis. The results showed that C/C composites belong to porous frac- tal structure. The fractal dimensions increase on the whole with decreasing porosity as the densifica- tion proceeds. The fractal dimensions are influenced by the texture of pyrocarbon and decrease with increasing anisotropy from isotropic pyrocarbon to high textural one. Both the complicacy of pore structure and the textural morphology of pyrocarbon can be represented simultaneously by the fractal dimension. The pore evolution of C/C composites in the densification process can be monitored using fractal dimension. A fractal characterization approach was proposed to research pore microstructure evolution in car- bon / carbon (C / C) composites during the chemical vapor infiltration process. The data obtained from mercury porosimetry determinations were analyzed using the sponge fractal model and the thermo-dynamics relation The fractal dimensions of C / C composites at different densification stages were evaluated. The pore microstructure evolution with densification time was studied by fractal dimension analysis. The results showed that C / C composites belong to porous frac- tal structure. The fractal dimensions increase on the whole with decreasing porosity as the densifica- tion proceeds. The fractal dimensions are influenced by the texture of pyrocarbon and decrease with increasing anisotropy from isotropic pyrocarbon to high textural one. Both the complicacy of pore structure and the textural morphology of pyrocarbon can be anoint simultaneously by the fractal dim ension. The pore evolution of C / C composites in the densification process can be monitored using fractal dimension.