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Oxidation behavior and structural changes of furan-resin-derived carbons heat treated at 3000°C were investigated at 500 and 700°C under dry air. Thermogravimetric analysis (TGA), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to detect and understand this behavior and the changes. Effect of tantalum on antioxidation property of Ta-alloyed carbon was also analyzed. The neat and Ta-alloyed carbons had insignificant weight losses even after being kept at 500°C for 12 h, while the Ta-alloyed carbon had weight loss lower than that of the neat carbon after being kept at 700°C for 6 h. It has been found by XPS that oxidation involves oxygen in internal area as well as on external surface of the carbons. It was also inferred that the carbon stored with oxygen in deeper internal area was easily oxidized. Ta alloying leads to change of the state of the Fermi energy on the specimens, which may cause the antioxidation property.