Plants have the ability to synthesize a wide variety of chemical compounds that are used to perform important biological functions, and to defend against attack from predators such as insects, fungi, bacteria and herbivorous mammals. The aim of this study was In vitro studding of antibacterial effects of the leaves and flowers methanolic extract of Anthemis gayana. In this study extract was obtained by by Soxhlet extraction for 8h. It was tested In vitro against 4 bateria. Several dilution of extract (62.5, 125, 250 mg/ml) was prepared. Antibacterial activity was tested by using microdilution MIC determination and agar well diffusion assay. Data were analyzed by ANOVA test in the P-Value< 0.05. The results illustrated that leaves extract in dilution 250 mg/ml has more inhibitor activity and most activity were shown against Pseudomonas aeruginosa (clinical). The results of the present project indicate that the Anthemis gayana leaves and flowers inhibited bacteria growth but their effectiveness varied. These antibacterial activities are likely due to the presence of the phenolic compound in the extract. Therefore we will be able perform researches with extraction of this plant effective compound for the treatment of infectious disease.