Chitosan is the only natural occurring basic poly saccharide containing amino groups

which shows favorable biocompatibility

low-toxicity

biological degradability

and is suitable for preparing micro spheres. In this paper

the preparation methods of chitosan micro spheres are reviewed

which include spray drying

emulsion crosslinking

layer-by-lay er self-assembly

interfacial polyme rization

solvent evapo ration and ionotropic gelation method. The advantages and disadvantages of different methods are discussed. Chitosan microspheres can immobili zed enzyme or cells

and has wide prospect in application for carrier drugs. The application of chitosan micro spheres in immobilized enzyme or cells and embedding drugs is also reviewed.