Abstract: 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∶〖KG-*2〗30, ultrasonic power 50 W, and time 50 min, and the extracting rate of leaves is 1062 %. Under 〖JP2〗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).

Key words: total falconoids of Mikania Micrantha leaves , ultrasonic assistant extraction , antibacterial activity