An aromatic heterocyclic Schiff base neodymium complex bearing thiazole was synthesized and its activity in the ring-opening polymerization of ε-caprolactone (CL) was examined. The conditions of the CL/Nd molar ratio, monomer concentration, polymerization time and temperature were investigated. Activities of ca.171 kg/Nd·h were obtained under the optimum condition (CL/Nd = 1600 (molar ratio), [CL] = 2.26 mol L－1, 1 h at 50οC), giving a poly(ε-caprolactone) (PCL) of number-average molecular weight Mn = 5.4 × 104 and molecular weight distribution MWD = 1.96. The conversion of CL monomer as high as 94% was observed after polymerized for one hour. The mechanism of coordination polymerization has also been illustrated.