Clay species of the Xuancheng red clay sediments were investigated using X-ray diffraction(XRD) method to understand the clay mineralogy and its genesis significance of the sediments in the middle to lower reaches of the Yangtze River, South China. The results show that soil layers of the laterite profile have similar clay mineral compositions of mainly vermiculite, illite, kaolinite, and mixed-layer clays. Mixed-layer illite-smectite and illite-vermiculite were also observed in the Xuancheng red clay sediments. The occurrence of abundant mixed-layer clays in the red clay profile suggests that the red earth sediments underwent overlap of deposit-weathering and multi-staged weathering processes. In the deposit-weathering pedogenesis process, the climate fluctuated between warm/seasonally dry and warm/humid conditions. The presence of mixed-layer illite-vermiculite in upper section indicates that the weathering degree of upper section is generally lower than that of the lower section.