A multi-arm star poly(DL-lactide) polymer was successfully synthesized with epoxidized soybean oil as an initiator. ESO accelerates the reaction rate of the ring-opening polymerization and a higher molecular weight PLA is obtained. ESO also improves the polymer's stability against hydrolytic degradation. Further- more, PLA modified with ESO can reduce the storage costs and prolong the service life of the polymer by minimizing monomer- induced autocatalysis during storage and usage.