A series of amphiphilic poly(L-leucine)-block-poly(ethylene glycol)-block-poly(L-leucine) (PLL-PEG-PLL) hybrid triblock copolymers have been synthesized. All the blocks in this system have good biocompatibility and low toxicity. The PLL-PEG-PLL copolymers could self-assemble into micelles with PLL blocks as the hydrophobic core and PEG blocks as the hydrophilic shell, which were characterized by FT-IR, H-1 NMR, and transmission electron microscopy analysis. The critical micellar concentration of we copolymer was 95.0 mg . L-1. The circular dichroism spectrum shows that the PLL segments adopt a unique alpha-helical conformation, which is found to play an important role in controlling the drug release rate. The drug release could be effectively sustained by encapsulation in the micelles. The copolymers may have potential applications in drug delivery.