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Chitosan (CS) was used as raw material to oxidize its C6 primary hydroxyl group to carboxyl group by laccase/2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) system to obtain oxidized chitosan (C-COS), and then reacted with C-COS and silver nitrate to obtain oxidized chitosan-Ag+ complex (C-COS-Ag). Fourier transform infrared spectroscopy (FT-IR), conductometric titration and X-ray photoelectron spectroscopy (XPS) were used to characterize four different bacteria as antibacterial templates, and UV spectrophotometer was used to optimized C-COS-Ag antibacterial conditions. The morphology of the bacteria before and after the addition of C-COS-Ag was observed by scanning electron microscopy (SEM). The results showed that when CS had a carboxyl group content of 1.42%, Ag+ existed in C-COS-Ag were [Ag(NH3)2]OH and Ag2O (one part was--COOAg and the other part was Ag2O) two forms. The optimal antibacterial condition of C-COS-Ag was 1 h and 26 ℃. The diameter of the inhibition zone was greater than 30 mm, and the minimum inhibitory concentration of Escherichia coli was 7.5 μg/mL. The minimum inhibitory concentration of staphylococcus aureus, salmonella and bacillus subtilis was 10 μg/mL. And the cell wall of the bacteria added with C-COS-Ag was damaged, which seriously affected the growth of bacteria. [ABSTRACT FROM AUTHOR]