Abstract: A high molecular weight poly (L-lactic-glycolic) (PLGA) was successfully synthesized by joining hydroxyl terminated prepolymer (OLGA-OH) together using 1,6-hexamethylene diisocyanate (HDI) as the chain extender. The polymer samples were characterized with FTIR, GPC, DSC, TGA and 1H-NMR. The results showed that the obtained polymer had a Mn of 5.6×104 and a Mw of 15.0×104 at -NCO/-OH=2 (molar ratio). The glass transition temperature (Tg) of the OLGA-OH was 36 ℃. After chain extension, Tg increased to 53 ℃.