Objective To review and analyze the properties, products, and appl ications of chitosan so as to explore the key molecular structure parameters which can affect the properties and appl ications significantly, and to reveal the relationship between molecular structures and properties so as to provide reference for further development of chitosan industryand scientific research. Methods Based on the collection and analysis of related l iterature, patents and medical productsderived from chitosan, as well as the author’s experiences in research and development, evaluation and standardization of chitosan, the paper was prepared to bring more attentions into the correlativity between structure and properties of chitosan. Results Potential risks in cl inical appl ication of chitosan-based preparations were seriously proposed in addition to a scientific review and analysis on relationships between chitosan structure and properties, as well as the present situations of developments and appl ications of chitosan. Conclusion The molecular structure is the crucial factor that can bring not only positive but also passive effects to the properties and appl ications of chitosan, especially for highly purified chitosan, molecular weight, and deacetylation degree are the most important parameters that should be focused more attention on.