Objective:To optimize extraction technology of astragaloside Ⅳ from Astragalus membranaceus by response surface methodology（RSM）.Method:Three-factor and three-level Box-Behnken experimental design was employed with ethanol concentration

flow rate and liquid-solid ratioas independence variables

extraction rate of astragaloside Ⅳ as dependent variable which was determined by HPLC-ELSD

experimental data obtained by multiple regression and binomial fitting of levels from independent variables

ethanol percocation extraction technology was optimized by RSM

and to predictive analysis.Result:Optimum extraction conditions were as follows:30% ethanol as solvent

flow rate 1.9 mL · min-1 · cm-2

liquid-solid ratio 6.5 mL · g-1.Under these conditions

theoretical value of extraction rate of astragaloside Ⅳ 1.50 mg · g-1

but measured value of 1.487 mg · g-1

it showed optimized technology model fitted well.Conclusion:Box-Behnken experimental design could be used for extraction optimization of percocation extraction process for A.membranaceus

optimized technology was simple and stable.