The phase behavior as well as the microstructures of the dodecyltrimethylammonium bromide (DTAB)/ sodium laurate (SL) aqueous two-phase system has been studied, By using FF-TEM, dynamic light scattering (DLS), a viscosity meter, and polarization microscopy, the effects of surfactant concentration and mixing ratio, temperature, salt concentration, and additives (octanol and toluene) on the phase separation have been systematically investigated. The phase separation is found to be strongly dependent on the variation of the surfactant aggregates. The different kinds of aqueous surfactant two-phase system can transit between each other upon the variation of the mixing ratio, the change of the salt concentration, and the addition of toluene and octanol.