POIY(L-lactide)-block-poly(ethylene glycol)-block-poly(L-lactide) (PLLA-PEG-PLLA) triblock copolymers were synthesized effectively by poly(ethylene glycol) initiated ring-opening polymerization (ROP) Of L-lactide under microwave irradiation. The products were characterized by H-1 NMR, GPC, and DSC. The experimental results have demonstrated that PLLA-PEG-PLLA triblock copolymer with a number-average molar mass of 28 230 g.mol(-1) and an L-lactide conversion of 92.4% could be synthesized after the L-lactide/PEG2000 reaction mixture was irradiated for 3 min at 100 degrees C. The L-lactide/PEG feed ratio had a strong influence on the microwave-assisted ring-opening polymerization, in which higher L-lactide/PEG feed ratios led to copolymers with higher molar masses and lower L-lactide conversions. Prolonged microwave irradiation at 100 degrees C did not change the molar mass of the copolymers significantly. The DSC study indicated that higher glass transition and melting temperatures were obtained for PLLA-PEG-PLLA triblock copolymers triblock copolymers via microwave heating was much faster than via conventional heating.