Abstract: A finite difference equation model was proposed for fabrication of unidirectional carboncarbon composites by Chemical Vapor Infiltration (CVI) process. The check experiment was designed to verify the accuracy of this model. The model results of density versus infiltration time showed good agreement with experiment data, which indicated that the model had good practicability. Moreover, much of the important information of CVI mechanism would be provided by the modeling results, such as the distribution of precursor concentration in preforms, uniformity of densification and evolving of porosity during infiltration.