Abstract: An analytical system for lysine(Lys), proline(Pro), leucine(Leu), alanine (Ala), histidine(His), threonine(Thr), methionine(Met), serine(Ser) and glycine(Gly) is established using the capillary zone electrophoresis indirect UV detection method. The experimental conditions including type, concentration and pH of buffer solution were studied in detail. The optimal experimental conditions were as follows:0.1 mol/L NaOH-14 mmol/L sulfanilic acid solution (pH=11.2) as the buffer solution, 20 kV as the separation voltage. The nine amino acids could be completely separated in 12 min. Furthermore, the content of the nine amino acids in Radix Pseudostell from different sources were successfully determined. The method showed good reproducibility, RSDs of migration time and peak height were less than 2.6% and 4.5% (n = 7), respectively.