Abstract: This study was designed to screen the excellent pore-forming agent in colon-specific membrane,and 5-aminosalicylic acid was selected as the model drug.Free membranes were prepared by film casting,among which cellulose acetate were used as the coating membrane material,chitosan,high ester pectin and calcium pectate were used as the pore forming agent,respectively.The permeability,swelling properties and colon-specific degradability of the free membrane were examined.The free membrane using calcium pectate as pore-forming agent owned the smallest permeability in gastric juice and small intestine fluid,and exhibited significant colon-specific degradability.Calcium pectate can be a good pore-forming agent for colon-specific preparation.