Mössbauer spectroscopy and X-ray diffraction were used to characterize iron oxide mineralogy and AL-substitution of goethite in clays of paddy soils derived from red earth and their original soils (red earth). The results showed that the types and properties of iron oxide minerals in paddy soils derived from red earth were obviously different from those of their parent soils. The main iron oxide minerals of red earth were hematite and high Al-substitutcd (>20 mol%) goethite, but the environments of paddy soil were unfavourable to the formation of hematite which might be transformed to low Al-substituted goethite or other forms of iron oxide after rice planting. The amount of Al-substitution in goethite in P horizon clays of percogenic paddy soil.was higher than that of other diagnostic horizon clays of paddy soil. Small particle, low-substituted(<15 mol%) goethite was the main iron oxide mineral in clays of W horizon in periodically water-logged paddy soil and in G horizon of gleyed paddy soil, no hematite was detected in these clays.The main type of iron oxide minerals and the change of Alsubstitution in goethite of paddy soils derived from red earth reflect the conditions and characteristics of paddy soil, Which are very signnificant for paddy soil classification.