The development of production and utilization technology of highly reactive coke is significant in order to improve blast furnace reaction efficiency. A basic study of the solution-loss reaction (C+CO2 -> 2CO) in a CO-CO2 atmosphere was performed with catalyst-supported high purity graphite to clarify the relation between the carbon and the catalyst. The presence of a small amount of CO (1.5%) in the CO-CO2 atmosphere greatly decreased the reactivity of the Ni-supported graphite at low temperature. On the other hand, the reactivity of the Fe-supported graphite increased with increasing CO until its concentration reached 50%. It was confirmed that the solution-loss reaction on the catalyst-supported graphite followed the redox reaction model and the changes in the reactivity with CO concentration could be explained by the equilibrium calculation based on the redox reaction model. It was also found that the complex Fe-Ni-supported graphite showed high reactivity from low temperature to high temperature in the CO-CO2 atmosphere. A SEM-EPMA observation revealed that the catalytic Fe-Ni particles did not agglomerate and were finely dispersed. On the other hand, in the case of a single-metal-supported graphite, the catalytic Fe or Ni particles agglomerated at high temperature, where the reactivity decreased. It was suggested that the complex Fe-Ni-supported graphite showed high reactivity because the agglomeration of catalytic particles was inhibited.