β-Carotene (β-C) is a well-established natural antioxidant agent, but its poor water-solubility, low chemi-cal stability and low bioavailability limit its application in food, pharmaceuticals and cosmetics industries.Thus it is critical to develop an efficient method to improve the water solubility and stability of β-C. In thisresearch, amphiphilic chitosan-graft-poly (lactide) (CS-g-PLA) copolymer was synthesized via a homoge-neous ring-opening polymerization (ROP) in ionic liquid. The obtained CS-g-PLA copolymer was able toself-assemble into about 14 nm micelles in water at low concentration, and β-C loaded micelles (β-C/M)had low β-C degradation after 15 days. The antioxidant properties of the β-C/M were investigated by the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) method and ferric reducing antioxidant power (FRAP) method, respectively. Significantly improved antioxidant activity was observed for β-C/M in compare with free β-C. The aqueous dispersion of β-C/M has potential to be applied in the field of functional food andcosmetics. © 2014 Elsevier Ltd. All rights reserved.