Abstract:Polysaccharide was extracted from Basella rubra L. using microwave -ultrasound assisted method. The difference of influence of ultramicro grinding and ordinary grinding on extraction rate was studied. And the ultramicro extraction conditions were optimized as well. The results demonstrated that： （1）there was 64.11 % increased in polysaccharide extraction rate for ultramicro grinding than that of the normal grinding technology under the same conditions； （2）The influence of liquid material ratio， time， ultrasonic power and microwave power on the polysaccharide extraction ratio from Basella rubra L. were investigated through the single factor experiment； （3）Box-Behnken Center design was used on the basis of single factor test to optimize the mi－ crowave-ultrasonic assisted extracting conditions of polysaccharide. The optimum conditions were determined as the microwave power was 331 W， ultrasonic power was 193 W， extraction time was 18 min， and the liquid-sol－ id ratio was 50 mL/g. The extraction rate could reach 27.39 % and the relative error was -2.35 % under the opti－ mum conditions， which was consistent with the theoretical value. So the model was proved to be effective to pre－ dict the actual extraction rate.