Abstract:The extraction of flavone from onion by ethanol/dipotassium hydrogen phosphate aqueous two-phase system was studied in this paper. The impacts of ethanol mass fraction，dipotassium hydrogen phosphate mass fraction，onion powder dosage，extraction temperature and extraction time were examined firstly. The optimum extraction conditions were optimized by response surface experiment. The results showed that the optimum extraction conditions for ethanol/dipotassium hydrogen phosphate aqueous two -phase system to extract flavonoids were as follows：ethanol concentration of 41.8 %，dipotassium hydrogen phosphate concentration at 22 %，feeding 0.24 g onion powder，extraction temperature at 50 ℃，extraction time for 30 min，and the extraction rate of flavone from onion was 5.32%under these conditions.