Abstract: In order to explore the processing of total flavonoids extracted from Sonchus asper(L.)Hill by the microwave irradiation pretreatment and the antimicrobial activity of ethyl acetate extraction of total flavonoids extracts,orthogonal experiment based on the results of one-factor experiments was used to optimize the best extraction process,and the antibacterial activity was measured with reference to the CLSI standard with 5 bacteria,such as Pseudomonas aeruginosa(ATCC9027),Pseudomonas aeruginosa(PA1),Staphylococcus aureus(ATCC29213),Staphylococcus aureus(SA1)and Escherichia coli(ATCC25922). The results showed that,the best extraction process of the total flavonoids from Sonchus asper aerial parts were as follows:Microwave irradiation time 120 s,microwave power 350 W,ethanol concentration 60%,water bath temperature 70℃,the solid to liquid ratio 1:40 g/mL and the water bath time 60 min. Under these conditions,the flavonoid yield was 38.328 mg/g.The optimal conditions of the underground parts were as follows:Microwave irradiation time 90 s,microwave power 490 W,ethanol concentration was 70%,the solid to liquid ratio 1:30 g/mL,water bath temperature was 80℃ and the water bath time 90 min,the flavonoid yield was 7.232 mg/g. The ethyl acetate extracts of total flavonoids extract had certain antibacterial activity. The MIC of SA1 were 4(aerial part)and 8 mg/mL(underground part),respectively. When the concentration was lower than 16 mg/mL,it had no inhibitory effect on Pseudomonas aeruginosa(ATCC9027 and PA1)and Escherichia coli(ATCC25922). Microwave assisted extraction had significant effect on the extraction of total flavonoids from Sonchus asper and the ethyl acetate extracts of total flavonoid extract had a certain inhibitory effect on Staphylococcus aureus.