Abstract: The predominance diagram and Pourbaix diagram of dissolved species of the Fe-H2O system with different iron concentrations were studied at 25 ℃ by a concentration comparison method.The concentration of dissolved species，border- lines for liquid phases or solid phases and borderlines between the liquid and solid phase were calculated on the basis of thermodynamic analysis and electrochemical analysis with total Fe concentrations of 1.0×10-2 mol/L and 1.0×10-5 mol/L.The predominance diagram of dissolved species and the Pourbaix diagram of the Fe-H2O system were then plotted.Comparisons made between predominance diagrams for different iron concentrations showed that at a specific temperature and pressure the total concentration of iron had little effect on the stable predominance regions of Fe3+，Fe（OH）2+， HFeO2， and FeO2-.But these conditions had a remarkable effect on Fe2+，HFeO2-，and Fe（OH）+.A series of hydroxylation reactions may occur with Fe（OH）2 and Fe3O4 with the decreasing of the total iron concentration and with the enhancement of basification. A higher total concen- tration of iron will result in a larger stable area and a more stable quality of Fe（s），Fe3O4（s），Fe（OH）2（s），and FeOOH（s）.

Key words: different iron concentration, Fe-H2O system, predominance diagram, Pourbaix diagram, concentration comparison method