epsilon-Poly-l-lysine (epsilon-PL) is a natural preservative for food processing industry. A thermo-responsive polymer, attached with Cu2+ or Ni2+, was prepared for metal-chelate affinity precipitation for purification of epsilon-PL. The low critical solution temperatures (LCSTs) of these polymers were close to the room temperature (31.0-35.0 A degrees C). The optimal adsorption conditions were as follows: pH 4.0, 0 mol/L NaCl, ligand density 75.00 mu mol/g, and 120 min. The ligand Cu2+ showed a stronger affinity interaction with epsilon-PL and the highest adsorption amount reached 251.93 mg/g polymer. The elution recovery of epsilon-PL could be 98.42% with 0.50 mol/L imidazole (pH = 8.0) as the eluent. The method could purify epsilon-PL from fermentation broth and the final product was proved as electrophoretic pure by SDS-PAGE. Moreover, these affinity polymers could be recycled after the purification of epsilon-PL and the recoveries were above 95.00%.