With the falconoids extraction rate as index

total flavonoids from Mikania Micrantha leaves were extracted by the ultrasonic assistance method，and the extraction process was optimized by the orthogonal design．Moreover

the in vitro antibacterial activity (inhibition zone diameter) and minimum inhibitory concentration (MIC) of the above product against Staphyloccocus aureus

Escherichia coli

Salmonella and Shigella were identified by the diffusion method and test tube method respectively．The results show that the optimum extracting conditions are as follows: ethanol concentration is 50%

the ratio of material to 1iquid 1∶30

ultrasonic power 50 W

and time 50 min

and the extracting rate of leaves is 1062 %. Under such conditions

the above extract of flavonoids has good antibacterial activities against Staphyloccocus aureus

Escherichia coli

Salmonella and Shigella

and the MIC is 1.562 5

1.562 5

3.125 0

3.125 0 mg/mL respectively (calculated through the flavonoid quality concentration).