Abstract: In this study,the effect of ratio of material to liquid,mass concentration of Na OH solution,extraction temperature,microwave power and extraction time on extraction rate of Coix starch was studied by ultrasound-microwave synergistic extraction.Based on single factor experiments,the Coix starch optimized by response surface methodology was obtain of various process parameters.The results revealed that the optimum extraction process parameters for ultrasound- microwave synergistic extraction of Coix starch included ratio of material to liquid of 1∶ 9( g / m L),the mass fraction of Na OH solution of 0.30%,extraction temperature of 34 ℃,microwave power of 134 W and extraction time of 150 min.In this optimal condition,the extraction rate of starch was up to93.15%,which was close to the theoretically predicted value by confirmative experiment,and the established model fitting degree was good.The method studied in this paper compared with traditional alkali extraction methods,microwave- assisted method and ultrasonic- assisted method,the extraction rate of Coix starch increased of18.97%,12.78%,10.35%,respectively.The ultrasound- microwave synergistic extraction is found to be timesaving and efficient which may be utilized for the extraction of Coix starch.