OBJECTIVE： To optimize the formulation of entecavir PLGA sustained-release microspheres， and explore its drug release in vitro. METHODS： PLGA sustained-release microspheres was prepared by emulsification-solvent evaporation method. Using composite score of entrapment efficacy and drug loading as indexes， orthogonal test was designed to optimize drug amount， drug-PLGA mass ratio， PLGA mass concentration， oil phase-aqueous phase volume ratio and polyvinyl alcohol （PVA） concentration； and validation test was also conducted. The prepared microsphere morphology， particle size and durg release in vitro were detected. RESULTS： The optimized formulation was entecavir 20 mg， entecavir-PLGA mass ratio 1 ∶ 10， PLGA mass concentration 200 mg/ml， oil phase-aqueous phase volume ratio 1 ∶ 10， and PVA concentration 2％； entrapment efficacy was （86.52±3.25）％， drug loading was （18.36±1.37）％， RSDs were lower than 5.0％ （n＝3）； it was round and smooth in appearance with average particle size of 58.35 μm； Q10 h， Q96 h and Q360 h were 9.6％， 42.9％ and 89.6％， and the drug release in vitro fitted to Higuchi model （r2＝0.965 8）. CONCLUSIONS： Entecavir PLGA sustained-release microspheres prepared by optimized formulation has good sustained-release performance.