The thermal protection structure made of ceramic materials like C/C and C/SiC are currently adopted in hypersonic and vehicle reentry system. In particular, C/C is used for its capability of resistance to high temperature range. There are few studies in literature related to the electromagnetic characterization of C/C and C/SiC in microwave ranges. This research is focused on the microwave absorption cross section (ACS) analysis of C/C and C/SiC in the range 800MHz-6GHz and 50GHz-63GHz. The use of reverberation chamber and vector network analyzer allows to compute the ACS thanks to the homogeneous distribution of the electromagnetic field within the chamber. A mechanical rotating stirrer is also used to increase the statistical homogenization of the electromagnetic field distribution in the testing environment. The results show that C/C and C/SiC possess high electric conductivity within this range of frequency, having absorption performances quite similar to that of metallic materials.