Abstract: In order to optimize extraction process of Siraitia grosvenorii flavonoids and study its antibacterial activity,the extraction process of S.grosvenorii flavonoids was studied by response surface method with the extraction time,extraction temperature,ethanol concentration and solid-liquid ratio as variables.Staphylococcus aureus,Bacillus subtilis,Clostridium sporogenes,Pseudomonas aeruginosa,Escherichia coli,Candida albicans,Aspergillus niger were used as tested bacterial strains in this experiment to explore antibacterial activity of Siraitia grosvenorii flavonoids and its MIC.The results demonstrated that the process of optimum extraction were ethanol volume fraction of 88%,extraction temperature of 80℃,extraction time of 118 min,solid-liquid ratio of 1:27(g/mL).Under these conditions,the extraction yield of Siraitia grosvenorii flavonoids was 5.6188 mg/g.It was very close to the analog values of 5.619 7 mg/g.The antibacterial experiments showed that Siraitia grosvenorii flavonoids had effective inhibition on 7 strains.The antibacterial activity was as follows:Aspergillus niger>Candida albicans>Staphylococcus aureus>Bacillus subtilis>Clostridium sporogenes>Escherichia coli>Pseudomonas aeruginosa.The MIC was as follows:0.25 g/mL to Escherichia coli and Pseudomonas aeruginosa,0.125 g/mL to Staphylococcus aureus,Bacillus subtilis,Clostridium sporogenes,0.0625 g/mL to Candida albicans,Aspergillus niger.This research results confirmed that the Siraitia grosvenorii flavonoids had antibacterial activity significantly.It provided reliable theory basis for Siraitia grosvenorii flavonoids to be a new natural preservative product.