A mouthwash composition comprises water and a modified polyglutamic acid composed of a plurality of segment A and a plurality of segment B randomly arranged, in which, the segment A has a formula I:The segment B has a formula II:wherein X═H, Na, K, NH4, ½Ca, or ½Mg, and Y═Cl, Br, or I. The modified polyglutamic acid in the mouthwash composition is 0.1-5 wt %. The mouthwash composition in the present invention can eliminate bad breath, and also has antibacterial properties, so it can suppress the formation of dental plaque and is effective in preventing periodontal disease.
