Abstract: Considering the relevant safety problems caused by microbial pollution, in order to improve the antibacterial properties of chitosan materials and its further application, this study modified chitosan (CS) materials with plasma under helium atmosphere to design CS-based antibacterial materials. In order to discuss the antibacterial properties and action mechanism of modified CS materials, which through antibacterial experiments, free protein/nucleic acid determination and so on. The microstructure of modified CS materials were characterized, and the results showed that after the CS materials were modified by helium plasma, the surface became rough, and the roughness was more obvious, The results also showed the -NH₂ of CS-based materials decreased from 83.32% to 72.10% and the -CONH₂ increased from 16.68% to 27.90%, related to the collision of charged particles during plasma modification. Moreover, in the antibacterial experiment, these CS-based materials showed excellent antibacterial properties to Escherichia coli (P<0.05) but for Staphylococcus aureus, there was no significant difference before and after modification (P>0.05). With the changes of chemical linkages, the cell membrane permeability of bacterium was significantly changed when contacted with the CS-based materials. There was also locally formed a negative environment to bacterium growth, which contributed to the antibacterial effect of materials.