Partitioning of several kinds of semi-synthetic cephalosporins in acetone/NaCl two-phase system was investigated. The system is composed of hydrophilic solvent, inorganic salt and water. The phase diagram of acetone/NaCl system was made by titration method. Cephalosporin concentration was determined by HPLC. Experimental results showed that cephalosporin concentration and temperature have a little effect on the partition of cephalosporins. NaCl concentration and acetone concentration affect the partition to a certain extent. When these concentrations increase, cephalosporins move from top phase (acetone phase) to bottom phase (salt phase). The effect of pH on the partition is great. At low pH, cephalosporins stay mainly in top phase. When pH increases to 3.8, most of cephalosporins transfer to bottom phase. It is practicable to extract cephalosporins by adjusting pH of the two-phase system. (C) 2012 Elsevier B.V. All rights reserved.