Block copolymers, poly(LLA-b-St)s and triblock copolymes, poly(LLA-b-St-b-MMA)s have been synthesized by the combination of the atom transfer radical polymerization (ATRP) with ring-opening polymerization (ROP) using bifunctional initiator (beta-hydroxylethyl alpha-bromoisobutyrate (HEBIB) without intermediate function transformation. The molecular weight (MW) and the molecular weight distribution (MWD) can be controlled. The structures of the copolymers were confirmed by H-1 NMR spectroscopy and GPC.