The paper presents the results of a calculation of the standard Gibbs free energy of the reactions of iron oxides reduction by carbon monoxide in the presence of carbon in the temperature range of 900–1600°K. A comparative thermodynamic analysis is made for the following reactions: interaction of iron oxides with carbon monoxide with the formation of carbon dioxide; interaction of iron oxides with carbon to form carbon monoxide, carbon dioxide; interaction of iron oxides with carbon and carbon monoxide to form carbon dioxide. The calculations are based on the principle of independence of the reactions in the system. The calculations of the change of the standard Gibbs free energy of reactions are made per mole of atoms of the initial substances (per mole of the system). It is shown that at temperatures higher than 1000–1100°K the reduction of iron from iron oxide(III), iron oxide(II,III) and FeO1+x’ occurs due to interaction with carbon monoxide in the presence of carbon. In the temperature range of 400–800°K, iron can be reduced from oxides through the interaction with carbon monoxide only.