Abstract: The pretreatment of Streptomyces albus fermentation broth was studied in order to obtain ε- poly- L-lysine in it.5mol / L Na OH was added into broth to adjust the p H8.5 in order to precipitate the protein,then 5ku polysulfone membrane was used in ultrafiltration,through which the most impurity protein was removed. The process conditions of ion exchange were also discussed in detail.The weakly acidic cation exchanger resin HD-2was selected as the best through static adsorption method with the adsorption capacity as index. The maximum adsorption capacity of ε- poly- L- lysine on HD-2 resin was 28.8mg / g.