Artemisia Herba – Alba is the one of the most important genus of Asteraceae family. It has numerous values because of medicine properties. Artemisia Herba – Alba has numerous application in traditional medicine from ancient times. In this research, antimicrobial effects of leaf aqueous, alcoholic extracts and essential oil of Artemisia Herba – Alba against Staphylococcus aureus PTCC 1431 and Escherichia coli PTCC 1399 were studied, using agar disc diffusion method. Methanol and ethanol extracts obtained from leaves of A. Herba – Alba exhibited antimicrobial activity against test microorganisms. In addition Artemisia herba-alba essential oil was inhibitory effects against all studied pathogenic bacteria. The results showed that essential oil of Artemisia herba-alba had the most inhibition diameter zone in Staphylococcus aureusthan E.coli (25-17mm successively). Therefore in this research we showed that the positive gram bacteria are more sensitive than negative gram bacteria. our results indicate the possibility of using essential oil in the treatment of bacterial infections, and the results of this study was encouraging, despite the need for clinical studies to determine of the real effectiveness and potential toxic effects in vivo