Abstract: PLLA-PEG-PLLA and PLLA-mPEG copolymers were synthesized via ring-opening polymerization of L-lactide using polyethylene glycol and methoxypolyethylene glycols as initiators, respectively. Their structures and molecular weights were characterized by ¹H-NMR. Micelles were prepared by direct dissolution or organic solvent evaporation, and the morphology and properties of the micelles were determined by TEM, DLS and dye probe techniques. The micelles formed have low CMC and are spherical in shape with sizes around 100 nm. The micellar diameter strongly depends on copolymer composition. The diameter of PLLA-PEG-PLLA micelles is smaller than that of PLLA-mPEG micelles, and solvent evaporation can result in smaller micelle size than direct dissolution. The in vitro study of Urapidil hydrochloride release indicates that drug loading efficiency and drug releasing rate are related to copolymer composition and preparation methods. The micelles show excellent sustained-release capability for Urapidil hydrochloride.