The quasi-ternary phase diagrams for microemulsion systems containing sodium dodecyl sulfate（SDS）,n-butanol,oil phase（n-octanol,n-octane,n-heptane,n-hexane） and water were plotted by the titration and electrical conductivity.Effects of oil type,mass proportion of surfactant and co-surfactant upon the forming of O/W microemulsion were investigated in terms of the region for O/W microemulsion in the phase diagram.Physical and chemical parameters including electrical conductivity,interfacial tension and viscosity were used to elucidate the phase behaviors and characteristics of microemulsion systems.According to the microemulsion phase diagram,the chromatographic conditions were optimized.A rapid and robust separation method was developed and validated for the determination of Amoxicillin-Sulbactam Pivoxil tablets.Good suitability and separation selectivity of HPLC were obtained.