Rosmarinus officinalis is a medicinal plant. It was analyzed for its phytochemical constitution, antibacterial activity and antioxidant activity. For this purpose, we use the Rosmary of Khirane province of Khenchela (Algeria). The tests of phytochemical screening showed that the plant contain flavonoids, tannin saponins, mucilage, and polyphenols. Conversely, alkaloids and coumarin was absent. The reported extraction of phenolic compounds was 9.3%, while the methanolic extract was found to contain 129.55 mg of polyphenols and 92.5 mg of flavonoids, indicating a rich content of these compounds in the extract .The extracting rosemary essential oil yielded 11 ml, which corresponds to a 2% yield. The antibacterial activity was determined against E. coli and staphylococcus aureus, The results reveal differential sensitivity patterns between the two bacterial strains. Both exhibited resistance to the negative control (distilled water) while showing pronounced susceptibility to the essential oil (17 mm inhibition zone for Staphylococcus and 19 mm for Escherichia coli) and antibiotic. Notably, the methanolic extract's effectiveness varied between the strains, being inactive against Staphylococcus but mildly effective against E. coli. The results showed that the highest mean inhibition zone was observed in the methanolic extracts. Our findings demonstrate significant antioxidant activity of rosemary, with a value of 0.45 mg/ml.