Abstract: The equimolar mixed system of decyltriethylammonium bromide and sodium decylsulfonate, which was homogeneous solution even with the total surfactant concentration increasing up to 0.2 mol•L－1, formed aqueous two-phase system(ATPS) when salts, such as NaF, Na2SO4 or Na3PO4, were added. The phase behavior and partitioning of BSA in this saltinduced ATPS were studied. Compared with the usual ATPS of catanionic surfactant mixtures, this salt-induced ATPS exhibited some special advantages, and overcame some shortcomings of the usual ATPS. It was shown that the phase behavior of this salt-induced ATPS could be adjusted by adding salts and the partition coefficient of BSA could be altered and optimized by salt species.

Key words: Catanionic surfactant mixtures, Aqueous two-phase system(ATPS), 　Protein partitioning