Abstract: On the basis of studying the properties of humic acids from soil and decomposed corn stalk and manure such as pig manure and chicken manure, the characteristics of complexes between iron and humic acids and the anti-oxidation of chelated iron was researched. The results showed that humic acids from cumulic cinnamon soil were belong to type A, and humic acids from decayed organic materials were belong to type RP. The ability for complexing of humic acids of type A was stronger than that of type RP. The higher stability of the complexes was , the stronger anti-oxidation of chelated iron(Fe2+) was. The availability of iron complexing with humic acids were higher than inorganic iron (FeSO4).