Under the nitrogen atmosphere, carbothermal reactions of calcium oxide and magnetite began at about 900 and 820 degrees C, respectively. Above about 1200 degrees C, CaO reacted with carbon to form CaC2, and the interaction between carbon and CaO was dominant. At the temperature range of 820-920 degrees C, Fe3O4 was reduced quickly to Fe. After the process, with the increase of the heat-treatment temperature, Fe reacted with carbon to produce the eutectic compound of Fe and carbon (FexCy) and the mole ratio of C and Fe in FexCy became larger and larger but no Fe3C was presented. At the low-temperature range of 950-1100 degrees C, calcium oxide and magnetite separately presented a catalytic action on the reactivity of carbon and the mixture of calcium oxide and magnetite had a cocatalytic effect on the carbon reaction with CO2. Under the CO2 atmosphere, the carbothermal reactions of metal oxides were restrained in the temperature range (950-1100 degrees C) above the point, at which the carbothermal reaction of metal oxides started to take place under the N-2 atmosphere.