Microsphere-based therapy has attracted a booming interest,because this system allows protein drugs to be protected from enzyme digestion and precisely delivered to the specific lesion site.Unfortunately,microspheres prepared by conventional methods have a broad size distribution,and it is rather difficult to control the particle size during the preparation.Consequently,poor reproducibility of the experiments and possible side-effects in therapeutic applications might arise,which prevent the microspheres from practical application.As we know,the demands on drug release behavior vary from case to case in clinic therapy.It is therefore highly demanding but challenging to prepare uniform-sized microspheres with different structures and attain the desirable drug release profiles for their different clinic applications.Chitosan,the second abundant polysaccharide next to cellulose,has been adopted to have potential application as a protein drug carrier due to its outstanding properties of non-toxicity,biocompatibility,biodegradability,mucus-adhesion and low cost.In this study,uniform-sized chitosan microspheres with various structural properties were successfully prepared by the SPG (Shirasu Porous Glass) membrane emulsification method.These as-prepared chitosan microspheres with controllable size make them promising for realizing reproducibility,more repeatable release behavior and higher bioavailability and passive target ability.The wellcontrollable structural properties of surface charge distribution,cavity size and wall porosity also enable them to cater tospecific demands from the applications as protein drug carriers.