C Chitosan is a compound which is obtained by exctraction of chitin fromshells of ocean creatures such as crutaceans, insects and also plants such asfungus. Chitosan plays a key role in inhibiting the growth of harmfulmicroorganisms including Staphylococcus aureus, a bacteria which resides in ourmouth. This is a positive gram bacteria, that bacteria have a irregular structurelooks like a grape. Staphylococcus aureus causes facial, periapical or peridontalabses and denture sore mouth. This research was carried out to test theeffectiveness of antibacterial activity of chitosan which inhibits the growth ofStaphylococcus aureus. These bacterias were observed at different degrees ofdeacetylation (89% and 93%) with concentrations (0,25%, 0,5%, 0,75%, 1% and1,25% of chitosan) and were incubated for 24 hours using disc method. The resultof this research showed inhibition zones where Staphylococcus aureus did notgrow in several degree of deacetylation and concentrations. At 89% degree ofdeacetylation the biggest zone formed was found in the disc containing 1%concentration of chitosan, forming 15mm of inhibition zone while the smallestone was found in 0,25% concentration with 11mm of inhibition zone. While in thecase of 93% degree of deacetylation, the biggest inhibition zone formed in thedisc containing 1% of chitosan concentration, forming slightly larger 15.3mm andthe smallest being 13,3mm at 1,25% of chitosan concentration. Other inhibitionzones at different deacetylation degrees showed small differences eventhoughstatistically they weren't significant.