OBJECTIVE: To investigate the nasal absorption regularities of psoralen and isopsoralen of different concentrations. METHOD: Building an experimental model of rat in situ nasal recirculation and determining the contents of psoralen and isopsoralen by HPLC. RESULT: The nasal absorption of psoralen and isopsoralen fitted in with zero order kinetics, getting saturated with the increase of concentration. CONCLUSION: A suitable concentration is necessary for the preparation of nasal remedies psoralen and isopsoralen.