The purpose of this study is to develop a novel measurement technique for in situ monitoring of the degradation processes of high temperature materials in combustion fields. Spatially, spectrally and temporally resolved images of emission from diatomic molecules in an acetylene-air flame were observed by a spectrovideo camera, which was assembled by combining a monochromator and a high speed UV video camera. Two-dimensional atomic absorption spectrometry (2D-AAS) using the spectrovideo camera was applied to investigate the degradation processes of C/C composites in an acetylene-air flame. The test samples employed in this study were three different C/C composites with Mg-doped oxidation-resistive double coating layer of SiC and glass materials, and C/C substrate. The result indicated that the temporal changes in the spatial distribution of atomic absorption by Mg atoms proved to be a good measure for in situ monitoring of the degradation/oxidation processes of the coating layer and substrate of C/C composites in high temperature fields.