OBJECTIVE： To study in vitro bacteriostatic activity of the extracts from Miao medicine Polygonum runcinatum. METHODS： Using chloramphenicol and fluconazole as positive control， the inhibitory effects of water extract， 95％ ethanol extract and its ethyl acetate and n-butanol fraction on 9 kinds of strains were determined by cup plate method， such as Staphylococcus aureus， Escherichia coli， Shigella flexneri， Salmonella typhi， Bacillus subtilis， Pseudomonas aeruginosa， type B Hemolytic streptococcus， Candida albicans and Cryptococcus neoformans. The parts with bacteriostatic activity and trial strains sensitive to drug were screened. Micro-broth dilution method and agar culture medium plate method were used to determine MIC and MBC of 95％ ethanol extract and its fractions of P. runcinatum to sensitive strains. RESULTS： The water extract of P. runcinatum almost had no inhibitory effect. 95％ ethanol extract showed different degrees of bacteriostatic activity to strains； bacteriostatic effects of it to 6 kinds of bacteria as S. typhi was better than that of type B H. streptococcus and 2 kinds of fungus. The ethyl acetate and n-butanol fraction of 95％ ethanol extracts showed good bacteriostatic effect and the ethyl acetate fraction had stronger effect， while all the fractions of 95％ ethanol extracts showed no inhibitory effect on fungus. MIC and MBC of 95％ ethanol extract to above 6 kinds of bacteria were 6.25-12.5 and 12.5-25 mg/mL， respectively； MIC and MBC of ethyl acetate fraction were 3.13-6.25， 6.25-12.5 mg/mL； MIC and MBC of n-butanol fraction were 6.25-12.5， 12.5-25 mg/mL. CONCLUSIONS： 95％ ethanol extract， ethyl acetate and n-butanol fractions of Miao medicine P. runcinatum have obvious in vitro bacteriostatic activity to 6 common bacterias as S. typhi.