ε- Polylysine is a light yellow powder with strong hygroscopicity and a slightly bitter taste. It is a straight chain polymer of lysine. It is not affected by pH value, is thermally stable (120 ℃, 20 minutes), and can inhibit heat-resistant bacteria, so it can be heat treated after addition. However, when encountering acidic polysaccharides, hydrochloride salts, phosphates, copper ions, etc., their activity may be reduced due to binding. When combined with hydrochloric acid, citric acid, malic acid, glycine, and higher fatty glycerides, it has synergistic effects. Molecular weight between 3600-4300 ε- Polylysine has the best antibacterial activity, and when its molecular weight is below 1300, ε- Polylysine loses its antibacterial activity. Due to the fact that polylysine is a mixture, it does not have a fixed melting point and begins to soften and decompose above 250 ℃. ε Polylysine is soluble in water and slightly soluble in ethanol. The infrared spectrum analysis of its characterization shows that there are strong absorption peaks at 1680-1640cm-1 and 1580-1520cm-1.