Staphylococcus aureus is a ubiquitous bacteria that causes a serious health problem because of its multi-resistance to antibiotics. The aimed of this study was to evaluate the antibacterial activity of P. kotschyi root against S. aureus ATCC 29213 and S. aureus, a clinical strain. The phytochemical compound was sought in the extracts by standard staining tests and extractions were carried out by fractionation using solvents depletion method with increasing polarity. The method of dilution in liquid medium was used for the antibacterial tests. The results showed that the aqueous extract of the bark was effective against both S. aureus with MICs of 0.39 mg.mL-1. The MICs of ethanolic extract were 0.39 and 0.78 mg.mL-1, respectively on S. aureus ATCC 29213 and S. aureus. The steles of P. kotschyi roots were less effective. The ethanolic and aqueous extracts at concentrations = 2MICs, have been respectively bacteriostatic and bactericidal effects on tested germs. The kinetics of inhibition showed that the aqueous extract of the bark at 0.78 mg.mL-1, completely destroyed the two germs respectively in 4 h and 5 h. The action of ethanolic extract at 0.78 and 1.56 mg.mL-1 occurs late against both S. aureus at 6 h and 7 h. Phytochemical screening revealed the presence of alkaloids, tannins, flavonoids, anthracenes, glycosides, saponosides and sterols, some of that may be responsible for the observed antimicrobial activity. This study proved the antibacterial activity of P. kotschyi roots that can be exploited as an antibiotic in the treatment of S. aureus infections.