The effects of Cinnamon granules on pharmacokinetics of berberine in Rhizoma Coptidis granules in healthy male volunteers, and the compatibility mechanism of Jiao-Tai-Wan (JTW) composed of Rhizoma Coptidis granules and Cinnamon granules were investigated. The concentration of berberine in plasma of healthy male volunteers was determined directly by high performance liquid chromatography (HPLC) after an oral administration of Rhizoma Coptidis granules alone or combined with Cinnamon granules (JTW). The plasma concentration-time curves of berberine were plotted. The data were analyzed with Drug and Statistics (DAS) 2.0 pharmacokinetic program (Chinese Pharmacology Society) to obtain the main pharmacokinetic parameters. The results showed that the plasma concentration-time curve of berberine was described by a two-compartment model. The C-max, T-max, t(1/2) and CLz/F of berberine in Rhizoma Coptidis granules were 360.883 mu g/L, 2.0 h, 3.882 h, 119.320 L.h(-1).kg(-1) respectively, and those of berberine in JTW were 396.124 mu g/L, 1.5 h, 4.727 h, 57.709 L.h(-1).kg(-1) respectively. It was suggested that Rhizoma Coptidis granules combined with Cinnamon granules could increase the plasma concentration of berberine, promote berberine absorption and lengthen the detention time of berberine in healthy male volunteers.