The extraction process of flavonoids from Cornus officinalis leaves was optimized by response surface methodology,and its antioxidant and antibacterial activity were studied in vitro.The extraction rate of flavonoids was the highest under the conditions of ultrasonic power 290 W,solvent to solid ratio 31∶1(mL/g),ethanol concentration 61% and extraction time 23 min,reaching 6.31%,which was consistent with the predicted value of the model.The results showed that flavonoids from C. officinalis leaves had a strong antibacterial activity against Salmonella typhimurium and weak antimicrobial activity against Pseudomonas aeruginosa,Staphylococcus aureus and Rhizopus chinensis,indicating that the flavonoids had a strong inhibitory effect on bacteria and weak inhibitory effect on fungi.The clearance rates of DPPH radical and hydroxyl radical were 77.24% and 83.54%,respectively,when the concentration was 1.2 mg/mL.The IC₅₀ of DPPH radical and hydroxyl radical were 0.699 and 0.631 mg/mL,respectively,which indicated that the flavonoids from C. officinalis leaves had strong antioxidant activity.