Taking pomelo leaves as the research object, the total flavonoids of pomelo leaves were extracted with the aid of ultrasound, and its antioxidant and antibacterial abilities were explored. The results showed that the optimal extraction conditions for flavonoids from pomelo leaves were ethanol volume fraction 80%, ultrasonic time 50 min, solid-liquid ratio 1∶25 （g/mL）, and the flavonoid content under these conditions was 11.746 mg/g. The antioxidant test results showed that the total reducing power of the preliminary extraction of pomelo leaf flavonoids was about 1.25 times that of the same mass concentration of ascorbic acid. In addition, the inhibitory effect of pomelo leaf flavonoids on Escherichia coli, Salmonella typhimurium and Staphylococcus aureus was Staphylococcus aureus> Escherichia coli> Salmonella typhimurium, and the minimum inhibitory volume fraction （MIC） was 0.074 mg/mL. In conclusion, the flavonoids of pomelo leaves have good antioxidant and antibacterial abilities.