Polysaccharides have attracted wide attention due to their renewable, biocompatibility and low cost. The objective of this research was to study the effect of cold plasma treatment on the properties of sodium carboxymethyl cellulose and sodium alginate. The viscosity, pH, total viable colonies and 1,1-diphenyl-2- picrylhydrazyl values were determined. Besides, the structures and mechanisms of sodium carboxymethyl cellulose and sodium alginate were also discussed. Results indicate that sodium carboxymethyl cellulose and sodium alginate modified with cold plasma treatment obtained antimicrobial and antioxidant ability. This is mainly attributes to the energy produced during plasma treatment breaks the molecular bonds within polysaccharides, meanwhile some active groups containing oxygen and nitrogen are introduced. Then the active groups could combine with the broken molecular band, lead to some functional properties. Compared with some traditional methods such as acid and alkali exaction, cold plasma treatment possesses stability and high efficiency, without any chemical pollution. Thus, cold plasma treatment provides a new method for the preparation of functional polysaccharides.