Objective To prepare nesiritide acetate sustained-release microspheres, investigate the property of in vitro drug release for the sustained-release effect, and reduce the frequency of drug use.Methods Nesiritide acetate sustained-release microspheres were prepared by double-elusion drying in liquid with PLGA as the carrier, Et acetate as the organic solvent, CMC water solution as the dispersion medium and mannitol as the diluents, and freezing drying.The prescription and preparation process were optimized by orthogonal test with particle size, yield and encapsulation as the indexes.The property of in vitro drug release was determinedWe calculated the cumulative drug-releasing percentage of sustained-release microspheres and obtained the drug-releasing curve.Results The prescription and preparation process was screened according to the orthogonal test with a drug loading capacity of 37.3%, an encapsulation efficiency of 91.2% and a zeta potential of (-27.8±1.72) mV.The in vitro releasing profile was in accordance with Higuchi equation.Conclusion The nesiritide acetate sustained-release microspheres for injection have a long time release effect.