Abstract: The ultrasound extraction process parameters of total triterpenoids from fried Vaccaria segetalis and antibacterial activity was analyzed. On the basis of single factor experiments,with ethanol concentration,liquid to material ratio,ultrasonic temperature and ultrasonic time as independent variable,the total triterpenoids yield as response value,the ultrasound extraction process of fried Vaccaria segetalis total triterpenoids was optimized using Box-Behnken experimental design with four factors and three levels. The total triterpene extracts was tested against 10 species of common pathogenic bacteria through double dilution method. The results showed that the optimum extraction condition of ultrasonic assisted extraction was:Ethanol concentration 65%,ratio of solid to liquid 1:25 (g/mL),ultrasonic temperature 63℃,extraction 40 min. The yield of total triterpenoids under the optimum conditions was found to 1.24%±0.003%,which agreed with the predicted value of 1.28%. The total triterpenoids from fried Vaccaria segetalis had certain inhibitory effect on 10 common pathogenic bacteria,especially to Escherichia coli,Staphylococcus aureus,Streptococcus pyogenes and Streptococcus pneumoniae,the minimum inhibitory concentration(MIC)and the minimum bactericidal concentration(MBC)were between 1.25~5 mg/mL. The results suggested that the regression models were efficient and stable for total triterpenoids from fried Vaccaria segetalis,while the extraction had a strong broad-spectrum antibacterial effect.