Objective: To identify the structure of the main chemical constituents in Sini decoction prepared by different extraction methods by HPLC-MS. Method: The Sini decoction was prepared by boiling water extraction method and combination of active parts method.C18 (4.6 mm×250 mm

5 μm) column was adopted. The gradient mobile phase consisted of acetonitrile (containing 0.01% acetic acid) and 2 mmol·L-1 ammonium acetate solution (containing 0.01% acetic acid) at a flow rate of 0.6 mL·min-1; the column temperature was 30 ℃; the injection volume was 2 μL. MS conditions: positive mode

dryer flow rate: 10 L·min-1

atomizing air pressure: 30 psi

debris voltage: 70 V. Result: 28 and 30 chemical constituents were identified in traditional water decoction and active ingredients combineddecoction by HPLC-MS respectively. All of the constituents were classified according to their medicinal materials derivation. Conclusion: The experiment provide a basis for the determination of the active ingredients in Sini decoction.