The study on bacterial capsular polysaccharide is deeper with the development of the molecular biology, saccharide chemistry and immunology. Not only the character and structure of bacterial capsular polysaccharide was researched, but also the genes related to the synthesis, regulation and pathogenicity. This review focuses on the chemical structure, synthesis genes, mechanisms of the diversity, synthesis regulation, function, pathogenicity and application of the bacterial capsular polysaccharide. The research hot spots are also summarized to supply the basic theory and threads to study and apply bacterial capsular polysaccharide.