Abstract: The effect of low-level oxidation, defined as a weight loss less than 6% at 700℃-1300℃, on microstructure and volume change of 2D carbon/carbon (C/C) composites was measured by SEM and a micrometer. Results indicated that the oxidation rate of the C/C composites was linear. Higher temperature favored for surface oxidation, which leaded to an increased burn-off but a thinner oxidized layer. Lower temperature, however, favored in-depth oxidation, which led to a decreased burn-off but a thicker oxidized layer. Separation of the carbon fibers from the substrate could be seen, The tips of the fibers were sharpened and the volume of the composites decreased.