Objective: To probe the effects of Rhizoma Corydalis processed with different acids on both the content of tetrahydropalmatine and the analgesia by Rhizoma Corydalis. Method: The decoction amount of the tetrahydropalmatine was measured by HPLC. The pain threshold was measured separately before and after mice took the drug by means of the hot plate. Result: The different processing of Rhizoma Corydalis exerted a certain influence on the decoction amount of the tetrahydropalmatine. Rhizoma Corydalis and its different acid products had an analgesic effect on the mice causing pain by hot plate. Conclusion: Of all the acid products of Rhizoma Corydalis

acetic acid ones had the least satisfactory effect. The comparison between malic acid

hydrochloric acid products and acetic acid product was not clearly marked. The citric acid products and the tartaric acid products had a certain advantage over others.