Abstract: In order to obtain quality carbon fiber, it is necessary to get theinformation about the fiber processing.The paper here discribes the analysis of different processed carbon fibers on cross sections by the use of Scanning Auger Microprobe (SAM).The sample of carbon fiber is displayed on the scanning electron microscope(SEM) with the magnification of 10⁴ times and then tests are done within a single f fiber.The Auger line scanning and the point analysis for carbon fibers,with the tensile strength of 3.43 GPa, 3.13 GPa and 2.45 GPa, respectively,are taken.The difference of carbonization state between the skin and the core of a carbon fiber in the chemical reactions of different preoxidation and carbonization can be observed in both the intensity of the carbon signal and the shape of the Auger peaks.