The soil responses to climatic changes are a key problem in the studies of global change. Soils in the past provide a valuable record for the understanding of the relationship between the soil and the climatic changes. Here we report a case study to the red earth section at Jiujiang City in southern China. This section is about 15m in thickness, and consists of two pedogenic units. The upper part is a layer of yellowish silty clay, while the lower part a layer of red clay with yellow and white worm-shaped veins. Mass-balance equations applied to geochemical analyses reveal that the degree of weathering increased down-section and the concentration of resistate constituents decreased upward. A pronounced depletion of bases(Na, K) has been shown in the lower part of the section. This weathering trend is not observed in the loess sections in northern China, and is probably the results of Quaternary climatic changes in southern China and of the variations in dust input resulting from the deterioration over central Asia.