Abstract: A high performance liquid chromatograbphic method was established for the deter-mination of cholic acid and hyodeoxycholic acid in bezoar, Liushen pills ,Liuying pills and Niuhuang Xiaoyan pills. Bile acids were labelled with 1-bromoacetylnitrobenzene in acetonitrile using 18-crown- 6 as catalyst. Derivatized bile acids were separated and determined on uBondapak C₁₈column (3.9mm×300mm,8～10um),using methanol-acetonitrile -water(24:35:41) as mobile phase and mandrolone phenylpropionate as internal standard. Standard .Selection of condition of derivatization reaction, mobile phase optimization, determination of linearity range and check of intervenient factor have been made.The accuracy of the method was checked by recoveries.