This paper deals with the study on the types,properties and isomorphic substitution of Fe (Ⅲ) by Al(Ⅲ) of iron oxides in torrid red earths under different arid and hot conditions in youth China by using the Mossbauer spectroscopy.The Mossbauer spectra for the colloidal portion(<2μm) extracted from the surface layer of the four red earths studied indicated that the superharamagnetic state appeared at room remperature and the magnetic splitting six-line spectra was observed significantly at 80K.The resuits fitted with a computer show that hematite and goethite are predominant in iron oxides and commonly occur in small particles,reflecting the feature of tropical and subtropical soils.Also,the proportion of hematite and goethite in soil colloids varies considerably in different dry climates; the drier the soil,the higher the propor ion of hematite.