Abstract: A supercritical fluid extraction (SFE)method was developed for the extraction of dl-tetrahydropalmatine in Corydalis yanhusuo W.T. Wang and its patent preparations.Benzene was usedas a modifier of supercritical fluid CO₂.The sample was extracted by this supercritical fluid staticallyfor 5 min and then 3 ml dynamically at 40℃ and 42 MPa. An unmodified silica gel YWG columnwith reversed phase eluent was used to determine dl-tetrahydropalmatine in Corydalis yanhusuo W.T.Wang and its patent preparations.A mixture consisting of methanol and 2 mmol·L^-1 phosphatebuffer(pH 7.2)(75:25)was used as the mobile phase. The method is simple, rapid and precise, soit can be used for the extraction and determination of the alkaloids in other crude drugs andpreparatlons.