Drug was encapsulated in a novel copolymers of poly(lactic-co-glycolic acid) (PLGA) to investigate the sustained-release formulation of drug loaded polymer microspheres delivery system. Used a modified solid-in-oil-in-water (S/O/W) emulsion solvent evaporation method to prepare microspheres, its morphology and particle size distribution were estimated by scanning electron microscopy (SEM), the profile of in vitro drug release were assessed by High performance liquid chromatography (HPLC). Finally, an stable release buffer was utilized to obtain a detailed drug release profile, which was analyzed by HPLC also. Results showed that the microspheres morphology, encapsulation efficiency and the cumulative drug release efficiency were appropriate for veterinary medicine using. The modified preparation method was simple and optimized, PLGA microspheres with excellent controlled-release characteristics may serve as drug delivery carrier and may prolong the drug sustained-release effect.