Staphylococcus aureus is one of the most dangerous organisms that threatens the life of humans and animals alike. It has been found that people who suffer from chronic diseases such as diabetes, blood vessels, pulmonary and cancerous diseases are more susceptible to infection, in addition to ability resist antibiotics, which made fierce and dangerous. This staphylococcus aureus possessed the SAK gene, which acts as a bio stimulant that plays an important role in the process of analyzing blood coagulation, as it acts as an anti-plasmogen activator and is in the form of an equal compound of human plasmin. SAK consists of a chain of amino acids numbering 136 amino acids. The study aimed to isolate the SAK gene using amplification technique PCR and insert it into an ideal vectorPET21a. And he transferred it to one of the strains of the E.coli(BL21DE3) , stimulating the bacteria by adding IPTG, the purpose of obtaining the highest level of protein expression in an ideal time, then purifying the protein by affinity chromatography.