Abstract: The content of hydrous micas in the clay fractions of main soils in Fujian Province were estimated by X-ray diffraction method. The factors influencing the content of hydrous micas were discussed. Parent material is the major factor influencing the content of hydrous micas in clays. The soils developed from marine deposit, alluvial deposit and shale were richest in clay micas, while those derived from basic rocks were poorest in clay micas. The content of clay micas in the soils with higher weathering degree, such as lateritic red soil, red soil, yellowish red soil and yellow soil ,was generally low. C horizons, which has lower weathering degree than B and A horizons, usually contained more clay micas than A and B horizons. However, the accumulation of xenogenetic parent materials could result in higher content of hydrous micas in A horizon than B or C horizons.