Abstract: To provide basic knowledge and theoretical basis for the research and application of chitosan in various fields. The structure,properties,extraction methods and applications of chitosan in medicine,water treatment and as membrane materials in fruits,vegetables and meat products were reviewed. At the same time,the application prospect of chitosan is prospected. The unique physicochemical and biological properties of chitosan make it an excellent auxiliary material for drug preparation,and play an immeasurable role in the drug preparation. In addition,chitosan has good film forming,viscosity,antimicrobial property and suitable barrier after film formation that make it more prominent in fruits,vegetables,meat products and other areas of fresh-keeping applications. Chitosan is an indispensable raw material in most fields of research and application.