Staphylococcus aureus causes one of the most common types of chronic mastitis. Mastitis is an inflammation of the mammary gland with local and symptoms that occasionally result in a systemic infection. This disease has profound impact on animal welfare and milk quality. This study allowed us to determine the MLST and spa typing diversity of Staphylococcus aureus isolated from cases of bovine mastitis in the west Algeria. The first purpose of this work was to investigate the phylogenetic profile of Staphylococcus aureus by spa typing and Multilocus sequence typing (MLST) isolated from Mastitis subcliniques and clinical cases which were previously investigated by Mass Spectrometry Maldi-Tof and spa typing. The second purpose was to determinate the complex clonal of strains. In total, 213 quarters milk samples were collected from 56 dairy cows at 6 farms in the region of Oran, from 2011 to 2012. The quarter milk samples were bacteriological analyzed and scored using California Mastitis Test. The prevalence-isolated bacteria were Staphylococci (38.9%)