Abstract: The antibacterial activity and stability of the two natural antibacterial agents chitosan and dandelion extracts had been studied. The minimum antibacterial concentration of E. coli,Salmonella,S. aureus which were produced by chitosan and dandelion were determined,and the inhibition rate and inhibition zone diameterand at the MIC had been studied also. And antibacterial activity and stability of the two antibacterial mixtures had been determined too. The results showed that both chitosan and dandelion extract have some antibacterial activity to E. coli,Salmonella,S. aureus,and the mixtures of chitosan and dandelion extract have more antibacterial activity than the two substance had been used alone. The mixtures had been reduced in different temperature,p H and UV irradiation time,and antibacterial activity could be ketp well in 40⁶0 ℃,p H5⁷ and 20⁴0 minutes UV irradiation,the results showed that the antibacterial stability of the mixtures was very well.