Chitosan extracted from crustaceans is an amino polysaccharide. Due to the strong interaction between molecules, it can only be dissolved in solutions of organic or inorganic acids, which limits its application in many fields. At present, the water-soluble chitosan is an activated chitosan derivative-chitosan hydrochloride (chlorinated chitosan) developed by our company after special treatment. It is directly soluble in water and is a strong cationic chitosan derivative, which can promote the absorption of nutrients or drugs by somatic cells, it is also can be used as the agent to promote the absorption of hydrophilic drugs and natural nutritional products. It is being applied in the fields such as medical dressing and carrier, food and health care and cationic flocculant, etc.