This work aimed to compare the yields and to evaluate the in vitro antibacterial activity and phytochemical constituents of hexane, ethyl acetate, dichloromethane and methanol extracts of seven individuals of Rosmarinus Officinalis Var. Prostratus obtained by the ultrasounds. The statistical study shows that there is an individual effect on the yield and on the antibacterial activity of these extracts. The Phytochemical screening revealed that the flavonoïdes and tannins are present in important quantities in the ethyl acetate extract, especially in individuals 4 and 7.The results of the in vitro antibacterial activity show that the extracts have significant inhibitory effect against M. smegmatis, Bacillus and E.coli especially in individuals 4 and 7. These results suggest that the flavonoids and tannins can be responsible for the differentiation of the antimicrobial property of Rosmarinus Officinalis Var. Prostratus. The quantitative study (CMI) confirmed the results of the qualitative study and showed that the ethyl acetate extract of individuals 4 and 7 present the highest antibacterial effect.