Abstract: The three-exit extraction separation process(TESP) has been widely used in theseparation of rare earths. For the simultaneous separation of A/B/C, there are four kindsof TESP. Based on the static equilibrium of A, B and C. in extraction, formulae of theextreme values were derived for determing the separation parameters of the TESP. With computer simulation, parameters for the separation of Gd/Tb/Dy were determined.It is shown that Tb component has been richened from 4.5% to 53.5% with 98% recoveryin the experimental test.

Key words: Rare earth, Extractive separation, Simultaneous separation, Formula of extreme value