Ring-opening polymerization of l-lactic acid O-carboxyanhydride was catalyzed by 4-dimethylaminopyridine in the presence of polyols pentaerythritol (PER) or dipentaerythritol (DPE). A high yield and relatively high molecular weight of 4- or 6-arm star PLA were obtained. The reaction was observed to be conducted easily and controllably. NMR analysis revealed that the end of the star PLA chain is a hydroxyl group and the central core is a PER or DPE group. The crystallinity of star PLA is lower than that of linear PLA. The crystallinity of 4-arm star PLA is lower than that of 6-arm PLA. Compared with that of 4-arm star PLA, the molecular arrangement of 6-arm star PLA may be relatively more regular.