Y-shaped diblock copolymer polycaprolactone-block-(polystyrene)(2) [PCL-b-(PSt)(2)] was synthesized successfully by the combination of enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). CH3O-terminated PCL was synthesized firstly by eROP of epsilon-caprolactone (epsilon-CL) in the presence of biocatalyst Novozyme 435 and initiator CH3OH, subsequently the resulting PCL was converted to macroinitiator by the esterification of it with 2,2-dichloro acetyl chloride (DCAC). PCL-b-(PSt)(2) diblock copolymers were synthesized in an ATRP of the styrene with CuCl/2,2'-bipyridine as the catalyst system. The kinetic analysis of ATRP indicated a controlled/'living' radical polymerization. The structure and composition of obtained polymers were characterized with NMR, GPC and FTIR. The thermal behavior was characterized by differential scanning calorimetry (DSC).