ObjectiveTo prepare the docetaxel(DTX)-loaded nanoparticles based on poly(D, L-lactide-co-gly -colide)-block-poly(ethylene glycol) (PLGA-b-PEG-COOH)(DTX-NPs)and to evaluate their in vitro release property．MethodsPLGA-PEG was successfully synthesized and double emulsion solvent evaporation technique was used to prepare DTX-NPs. The size distribution, zeta potential, and surface morphology of the prepared DTX-NPs were characterized by dynamic light scattering (DLS) and transmission electron microscopy(TEM); the entrapment efficiency and drug content were investigated by HPLC; and the in vitro release was examined using phosphate buffer solution as the releasing medium. ResultsThe average diameter of DTX-NPs was (138.8±1.01) nm, the zeta potential was (-13.74±3.54) mV, the encapsulation efficiency was (99.91%±0.29%), the drug load was (2.47±0.02) μg/mg, the 24 h drug release was 49％, and the total drug release in 120 h was 95％. ConclusionThe present preparation method for DTX-NPs is reliable and simple, and the product is stable and possesses a sustained release character in vitro. It can stay in the blood for a long period and possess a bright future of application.