Objecitves: Peel of Citrus unshiu (Rutaceae) has been used in traditional herbal prescriptions. Hesperidin and naringin contents of Citri Unshii Pericarpium were determined and compared to herbal prescriptions. Then, the different extractions from prescriptions are explained with traditional herbal theories. Methods: The herb and herbal prescriptions were extracted in boiled water. A quantitative analysis was made of hesperidin and naringin using HPLC with-reversed-phase CIS column and a UV detector at 204nm. Elution was carried out at 1.0ml/min with $38\%$ methanol. Results and Conclusions: The extract of Citri Unshii Pericarpium for 180 min was the better method for extracting naringin and hesperidin. The flavonoid contents in remedies are different among several traditional herbal prescriptions. The reason for the difference can be explained with traditional drug interaction theories.