Objective: To prepare 20(S)-protopanaxadiol polylactic acid-glycolic acid(PLGA)microspheres. Method: 20(S)-protopanaxadiol PLGA microspheres were prepared by emulsion-solvent evaporation method

with polyvinyl alcohol(PVA)as emulsifier

mixture of ethyl acetate and methylene chloride as oil phase.Based on single factor test

with composite score of microspheres yield

encapsulation efficiency and drug-loading as index

formulation technology was optimized by orthogonal test

then to investigate its in vitro release characteristics. Result: Optimized formulation technology was as following:volume ratio of O/W 1:50

the mass fraction of PVA 0.5%

feeding dosage 20 mg.These prepared microspheres had round appearance with average particle size of about 1.16 μm

microspheres yield of 35.58%

encapsulation efficiency of 41.76%

drug loading of 19.61%.In vitro release of these microspheres within the first 0.5 h was 18.24%

and cumulative release was up to 98.99% in 192h. Conclusion: This optimized formulation and preparation technology was stable and feasible.These prepared microspheres had significant sustained release effect.