Nanofiltration was applied for desalting of aqueous extract of Acanthus ebracteatus Vahl. The optimal condition for the desalting was found to be at flow velocity of 0.875 m/min with applied pressure of 10 kg/cm 2 to obtain the average NaCl rejection of 31%. The diafiltration process comprised of 1.5 concentration followed by the diafiltration ratio of 2 allowed 80% salt removal. The mathematical model developed for the diafiltration process agreed very well with the experimental results. In addition, the aqueous extract of A. ebracteatus Vahl. after the removal of salts exhibited better cytotoxicity against both human epidermoid carcinoma and human cervical carcinoma.