Liuwei Dihuang, whose compatibility to prescription was well established as Traditional Chinese Medicine (TCM), has been demonstrated useful for the treatment of diseases in China. However, the absorption and effect of the raw plant materials of Liuwei Dihuang were not consistent. To optimize the physicochemical and medicinal characterization of Liuwei Dihuang, the raw plant materials of Liuwei Dihuang were ground to 161.9 nm particles by HSCS (High Speed Centrifugal Sheering) pulverizer. The nano particles were characterized by polarizing microscope and SEM. Paeonol was analyzed by HPLC (High Performance Liquid Chromatography). The plasma concentrations of paeonol were determined to evaluate the characterization of nano Liuwei Dihuang in rats. The results showed that the plant cell walls were broken into pieces and the extraction efficiency of paeonol was increased by 23.5% after nano pulverization. The maximal plasma concentration (c(max)) was increased from 32.7 mu g/mL to 61.6 mu g/mL, while the time (t(max)) to the maximum plasma concentration was decreased from 3.5 h to 1.5 h. Nano pulverization can obviously increase the absorption speed and absorbing capacity of Liuwei Dihuang in rats. (C) 2008 Elsevier B.V. All rights reserved.