The Red Earth Formation in the middle-lower Yangtze River is an important pedo-stratigraphical unit in southern China. This formation is among the best geological records of Quaternary environment that bear information of climate changes for the subtropical zone of China. The study on the origin of this formation is the basis for further investigation of the paleoclimatic information. In this study, grain-size was analyzed on the samples from Jiujiang section at Jiujiang City of Jiangxi Province, and the result was compared with that of the typical Quaternary eolian deposit, as well as the lacustrine and fluvial sediments. Grain-size distribution was determined with a Malvern Mastersizer 2000 particle analyzer with a precision less than 1%. The analysis on grain-size indicates that the Xiashu loess and vermiculated red soil (VRS) in Jiujiang section consist of uniform fine particles. The particles display a bimodal distribution, with grain-size fraction of 5～50 μm dominantly, and > 63μm in a small part.
