Abstract: Taking the heating process of recycling-gas for oxygen blast furnaces as a research background, carbon deposition behavior in heating at higher CO and H₂ volume fractions was investigated under a laboratory condition. The results indicate that temperature and CO₂ volume fraction are important factors for carbon deposition. In the temperature range of 300℃ to 700℃, the carbon deposition rate increases with the increase of temperature below 500℃, but deceases when above 500℃. The carbon deposition includes CO decomposition and carbon deposition reaction by the hybrid of CO and H₂, each possible role of which was analyzed through comparing the thermodynamic theory and experimental phenomena in the carbon deposition. The morphology of deposited carbon and the carbon deposition behavior in heating from 500℃ to 700℃ were investigated by scanning electron microscopy. In addition, the carbon deposition rate decreases gradually with the increasing of CO₂ volume fraction at 500℃ and 600℃, and this inhibition effect on the carbon deposition behavior is greater at 500℃.