Objective To construct the drug delivery system of gentamicin/chitosan microspheres for local injection, and evaluate its physicochemical properties and cell cytotoxicity.Methods Gentamicinwas used as model drug, chitosan as carrier, lecithinand hydroxypropyl-β-cyclodextrin as accessories, and the microspheres of gentamicin/chitosan/lecithin/hydroxypropyl-β-cyclodextrinwas prepared by spray drying method.The physicochemical properties and cell cytotoxicity of themicrospheres were investigated by UV spectrophotometry , scanning electron microscopy, X-ray diffraction, dynamic membrane dialysis and MTT assay.Results Five kinds of chitosan microspheres ( A, B, C, D and E) with different drug/carrier ratios were successfully prepared by spray drying method.The yield, drug loading and entrapment efficiency of the drug-loaded microspheres were 34.38%~46.94%, 10.20% ~18.67%, 61.20% ~74.72%, respectively.SEM results showed that compared with microspheres A, B and C, microspheres D and E own the spherical shape with wrinkled surface and uniform particle size, particle size between 0.5 ~3 μm, no adhesion.X-ray diffraction analysis showed that the drug was encapsulated in the microspheres.The results of in vitro release indicated that microspheres D had a good sustained release effect in the four drug-loaded microspheres.The results of cytotoxicity test showed that when the concentration of gentamicin reached 400 μg/mL, the relative growth rate of microspheres D was still higher than 80% with the cytotoxicity grade was one, ie, no cytotoxicity.Conclusion The microspheres D with good physicochemical properties, sustained-release effect and biocompatibility, is expected to be a good carrier of prostate local drug delivery.