Abstract: The star-shaped PLLA-SA copolymers with terminal carboxyl groups was synthesized successfully by the "core-first" method, and was dispersed into acetone to obtain PLLA-SA nano-dispersion. Then chitosan (CS) and dispersion were self-assembled via electrostatic action to form injectable CS/PLLA-SA complex hydrogel. The composition, structure and properties of PLLA-SA, PLLA-SA nano-dispersion and CS/PLLA-SA hydrogel were characterized by laser particle size and zeta potential analyzer, FTIR and SEM. The maximum zeta potential value of PLLA-SA was -21.89 mV. The average particle size of the PLLA-SA nano-dispersion was about 200 nm. Ibuprofen(IBU)-PLLA-SA nano-dispersion was prepared at PLLA-SA mass concentration of 5 g/L, the mass ratio between IBU and PLLA-SA of 1:2, stirring speed of 650 r/min for 1 h, then of 550 r/min for 5 h, and temperature of 15 ℃. When IBU-PLLA-SA nano-dispersion was mixed with 10 g/L chitosan hydrochloride (7 : 3 volume ratio), the hydrogel was reversible self-assembly formed，and the loading efficiency and loading content of the hydrogel can reach 85.38% and 28.46%, respectively. The in vitro study of drug release indicated that the injectable CS/PLLA-SA complex hydrogel exhibited a significant sustained-release capability for IBU, and the cumulative release rate of IBU could reach 95.81% within 30 h.