Six pure compounds were successfully isolated from n-hexane and ethylacetate extracts of the roots of Stemona collinsae plant (Stemonaceae family)collected in Laos by silica gel column chromatography and preparative-HPLC.Their structures were characterized as sesamin (1), stigmasterol (2), stemanthren C3), 2,2',5'-Trihidroxy-5-methyl biphenyl (4), 4-Hydroxy-3-methoxybenzaldehyde5) and stemanthren A (6) by 2D NMR spectroscopic analyses. Two compounds,stemanthrenes A, C were evaluated their antimicrobical activity against sevenstrains (Staphylococcus aureusBacillus subtilisLactobacillus fermentumSalmonella entericaEscherichia coliPseudomonas aeruginosa and Candidaalbican). The result showed that stemanthren C could inhibit the growth ofStaphylococcus aureus