Emodin (1, 3, 8-trihydroxy-6-methylanthraquinone) has been identified to have the potential to improve lung fibrosis and lung cancer.To avoid the liver and kidney toxicities and the fast metabolism of emodin, emodin-loaded poly(lactic-co-glycolic) acid microspheres (ED-PLGA-MS) were prepared and their characteristics were studied.ED-PLGA-MS were prepared by the organic phase dispersion-solvent diffusion method.By applying an orthogonal design, our results indicated that the optimal formulation was 12 mg/ml PLGA, 0.5% gelatin, and an organic phase:glycerol ratio of 1∶20.Using the optimal experimental conditions, the drug loading and encapsulation efficiencies were (19.0 ± 1.78) % and (62.2 ± 2.63) %, respectively.The average particle size was 9.68 ± 0.65 μm.In vitro studies indicated that the ED-PLGA-MS demonstrated a well-sustained release efficacy.The microspheres delivered emodin primarily to the lungs of mice upon intravenous injection.It was also detected by microscopy that partial lung inflammation was observed in lung tissues and no pathological changes were found in other tissues of the ED-PLGA-MS-treated animals.These results suggested that ED-PLGA-MS are of potential value in treating lung diseases in animals.