The mineral composition.of clay fraction(<2μ) of about sixty representative paddy soils was studied by X-ray diffraction,differential thermal analysis and chemical methods.It was found Chat in most paddy soils,the mineral composition resembled to the parent soils on which they had developed.For example,both the red soils derived from quartermary red clay and the corresponding rice paddy soils in the subtropic zone of central China possess kaolinite and illite as the predominant clay minerals with comparatively smaller quantities of quartz and montimorillonite."De-potassication" and "De-silication" are the manifest change of clay minerals during the development of paddy soil,where the illite-type clays are partially transformed into montimorillonite and further into kaolinite especially in soils rich in potassium-bearing minerals.