A HPLC method was established for the determination of psoralen and isopsoralen in Psoralea corytifolia L. and its preparations. Psoralen and isopsoralen can be separated on ?-Bondapak C15 column with a mobile phase of MeOH-H2O (6:4) and detected at 245nm. The optimum conditions based on experimental results was to extract the sample by MeOH in an ultrasonator for 30 min. The method is simple and accurate.