Objective: To study the antibacterial effect of Filifolium sibiricum(FS)and its possible mechanism preliminarily. Method : Vitro experiments using micro dilution method to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 12 species common clinical pathogens. The anti-microbial activity of FS was observed mice mortality within 7 days by injecting dry yeast suspension of bacteria in intraperitoneal. Antibacterial mechanism was investigated by transmission electron microscope. Result: FS had different levels of bactericidal effects to 12 species common clinical pathogens. Especially for drug-resistant Staphylococcus aureus

MIC is 0.43 g·L-1 and MBC is 0.86 g·L-1. In vivo high dose can protect animals infected by S. aureus

E. coli

Pseudomonas aeruginosa

drug resistant S. aureus and drug resistant Klebsiella pneumoniae. The dose group was still effect to P. aeruginosa and drug resistant S. aureus. Electron microscopy showed that FS can melt bacterial cell wall. Conclusion: FS antibacterial activity was superior than Shuanghuanglian oral solution in vitro to 12 clinical common pathogens

especially to drug resistant P. aeruginosa which the positive control group had no role. The vivo experiments results show that it has a protective effect to systemic infectied animal model

especially to drug resistant S. aureus infections still has a protective effect. It can destroy the cell walls of bacteria at the same time.