Abstract: The ablation performances of carbon /carbon composites with 3D fine woven pierced felt structure and carbon fiber needled bulk felt structure were respectively tested on an arc heater, and the morphologies of specimens were observed by scanning electron microscopy (SEM).The results show that the ablation process of C/C composites is controlled by chemical erosion and mechanical erosion and mainly by mechanical erosion. The surface roughness would be accelerated because of the existence of Z direction carbon fiber bundles, and the ablation rate of the C/C composite with 3D fine woven pierced structure is higher than that of the unidirectional carbon fiber needled bulk felt structure. In addition, because the unidirectional carbon fibers are perpendicular to the ablation flow, the C/C composite with the unidirectional carbon fiber needled bulk felt structure has good ablation performance.