The red earths originated from Quaternary red clay are widely distributed in the hilly lands of central Jiangxi Province. Some physical and chemical properties of different particle size fractions of red earths were investigated. The main results are summarized as follows: 1. The clay minerals of the fine clay fraction(<0.001 mm) in the soils are predominated by kaolinites and vermiculites and contain some hydromicas and interlayer minerals. Distinct difference in the distributions of clay minerals was found between the coarse clay fraction (0.002-0.001 mm) and the fine clay fraction(<0.001 mm). 2. Chemical analysis of the samples showed that the content of SiO₂ decreased, but that of Al₂O₃ increased with the soil particles size fraction changing from coarse to fine, Which are consistent with the reported results by foreign pedologists. The sand fraction contained more Fe₂O₃ and had greater hygroscopicity and swelling capacity as compared with the silt fraction. These results are similar to those of bleached and permeable paddy soils in the Taihu basin, but different from forengn reports. 3. Plasticity and swelling were found only in the clay fraction(<0.002 mm). But in foreign reports these characters could be found in 0.005-0.001 mm particle fraction of some upland soils, and it might result also from <0.002 mm fraction. 4. The compressive strength of red earth was found only in<0.005 mm size fraction, but that of paddy soils of the Taihu basin mentioned above was found in <0.05 mm size fraction. It is considered that the plasticity and compressive strength have an obvious relationship with the content of fine clay in the paddy soils of Taihu, but these properties are weakened as a consequence of microaggregates with high stability formed by fine clay and sesquioxides in clayey red earth. Above-mentioned investigation is only a beginning for the study of the physical and chemical properties of different particle size fractions in upland soils of China. The experimental results may promote our understanding of the basic properties of soil particles, and supply a scientific basis for particles size fractionation and textural classification of soils in China.