The synthesis of well-defined H-shaped block copolymer based on the enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP) is described. The dihydroxyl polycaprolactone (PCL) was synthesized by the eROP of epsilon-caprolactone (epsilon-CL) in the presence biocatalyst Novozyme 435 and initiator ethylene glycol. Subsequently, the resulting PCL was converted to tetrafunctional macroinitiator by the esterification with 2,2-dichloro acetyl chloride (DCAC). The H-shaped block copolymer was then synthesized by the ATRP of styrene. The polymers were characterized by NMR and GPC. Linear first-order kinetics, linearly increasing molecular weight with conversion, and low polydispersities observed from the ATRP of St showed that the polymerization was well controlled. (PSt)(2)-b-PCL-b-(PSt)(2) block copolymers with varying molecular weight and controllable composition were obtained.