Abstract: According to the principle of phase inversion, polysulfone micorspheres were prepared by mixing two emulsion systems.SEM photos showed that the diameter of microspheres was relatively even and the surface of microsphers was compacted.During the preparation process, the concentration of polysulfone in dimethylformamide (DMF) and the volume ratio of continuous phase (paraffin ) versus disperse phase (DMF or water) in the two emulsion systems had significant effect on the characteristics of microspheres.The polysulfone microspheres thus formed showed a good absorption both to the acid stimulant, furosemide and the alkaline stimulant, triamterene.