Abstract: More reasonable expressions for standard molar Gibbs free energy change of iron oxides reductions were obtained through conducting analysis on the decomposition thermodynamics of iron oxides，as well as on the correlation between decomposition thermodynamics and reduction thermodynamics，whereby the origin of the stepwise reduction sequence of Fe₂O₃ were revealed. The analysis showed that the stepwise reduction sequence of Fe₂O₃ stems from its decomposition sequence. The rules of the decomposition thermodynamics of iron oxides are completely parallel to its reduction thermodynamics. With 570 ℃ as the boundary temperature，the molar Gibbs free energy change of the iron oxides reductions varies in their magnitude sequence，resulting in the change of the coupling pattern of the reactions，and subsequently leads to the two different stepwise reduction sequences for Fe₂O₃，and two different reduction modes for Fe₂O₃.

Key words: Change of Gibbs free energy, Reductions coupling, Decomposition sequence, Fe2O3 reduction sequence, Fe3O4 reduction mode