Abstract: In this paper,the effect of objective factors to the antimicrobial activity of chitosan have been studied,in purpose to confirm the best conditions.St.aureus was used as experimental microbial and inoculated to broth substrate with certain chitosan.The effects of the acetic concentration,enviroment pH value and concentration,molecular weight of chitosan etc.were tested.The experiment showed that the antibacterial activity of chitosan with the same degree of deacetylation and molecular weight was increased with its concentration.Dissolving chitosan in 2% acetic and control the pH value of substrate at 6.0 had the best effect.Microwave radiation was taken to preparation the water-soluble chitosan,but its antibacterial activity decreased.

Key words: chitosan, antimicrobial, St.aureus