Objective: To prepare quercetin-poly(lactic-co-glycolic acid) block copolymer (QC-PLGA) nanoparticles freeze-dried powder and investigate its in vitro release rule. Method: QC-PLGA nanoparticles were prepared through emulsion solvent evaporation method

optimal formulation process was defined by means of orthogonal test.QC-PLGA nanoparticles mixed with the protective agent were freeze-dried

which was explored in vitro release rule through dynamic dialysis technology. Result: Optimum preparation parameters were as follows:polyvinyl alcohol (PVA) of 0.2%

PLGA of 10 g · L-1

proportion of oil and water phase of 1: 35

QC amount of 5 mg

2% lactose as freeze-drying protective agent.Surface of QC-PLGA freeze-dried powder was smooth without shrinking subsidence

which had dense structure.After the injection water was added to sway

redispersibility was good.The rule of in vitro release was in line with Weibull equation model

which was fitted the drug release kinetics equation of ln[ln(1/1-Q)]=0.399lnt-1.503 (R2=0.973). Conclusion: The preparation technology of QC-PLGA nanoparticle freeze-dried powder is simple and feasible

which is easy to store with stable properties.Compared with quercetin

QC-PLGA nanoparticle freeze-dried powder has an obvious sustained release effect.