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. Furthermore, 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.