In this work, the effects of pH and salt and its concentration in the excess aqueous phase on the back extraction efficiency of BSA (Bovine Serum Albumin) using a reverse micellar system, of which the organic phase contains AOT(sodium di(2-ethylhexy) sulfosuccinate) and iso-octane, was extensively examined. In this effort, BSA solubilized in the reverse micells by means of the phase-transfer method was back-extracted by bringing an excess aqueous phase into contact. When 1:1 salt such as KCl or NaCl was added, BSA could be effectively back-extracted to the excess aqueous phase at a pH higher than its isoelectric point pI.