Ring-opening polymerization of epsilon-caprolactone (CL) has been firstly achieved by a novel rare earth initiator of scandium tris(2,6-di-tert-butyl-4-methylphenolate), producing PCL with M-v of 75,700 in solution polymerization under mild conditions. Kinetics study indicates that the apparent activation energy is 58.0 kJ/mol. Mechanism study reveals that the monomer ring is opened via acyl-oxygen bond cleavage leading to a Sc-O active center.