The present paper discusses ultrasonic extraction method aided extraction of coumarin from a Mongolian drug, Chagan-sorlo (Radix Glehniae), aiming to study out how much coumarin contained in Chagan-sorlo, and to provide the scientific basis and production guidance for extracting coumarin from Chagan-sorlo. Under different conditions the coumarin in Chagan-sorlo was extracted by ultrasonic, measured and analyzed, and then HPLC was used to carry out the measurement. Result showed that with solvent volume fraction of 70%, extraction time of 20 min, ultrasonic power of 175 W, temperature of 25 ℃, solid-liquid ratio of 1∶20, and 80～100 mesh extraction, the coumarin extraction reaches the highest yield.