This article fully evaluated the SMA-ethanol as an enteric coating material from synthesis, characterization and film properties to tablet coating. Using styrene and maleic anhydride as the reactants, SMA copolymers were synthesized with different reacting condition. Both of the reacting and purification condition were optimized, and the characterization methods of the physicochemical properties such as molecular weight, molecular weight distribution and acid value were also established, based on which the pilot-plant-scale test of the synthesis of SMA was carried out. The effects of reacting condition to degree of esterification were evaluated, in which included the catalysts, the using amount of catalysts, the reacting time and the reacting temperature, the result indicated that the most fitting reacting conditions were as follow: MEK as the solvent, TEA as the catalyst, with the catalyst amount of 15-20%(mol percent), the reacting time was 8h with the reacting temperature of 80℃. SMA-ethanol with different degree of esterification had different pH-sensitive values; such polymers can be dissolved in different parts of the small intestine, which have a good perspective in the application of drug delivery system. This article also discussed the calculation of degree of esterification, the activity of catalysts and the mechanism of the esterification of SMA and ethanol catalysted by TEA. Free films were prepared by adding different kinds and amounts of plasticizers, the film surface topography was determined by a SEM, the tensile strength, water vapor transmission rate and moisture absorption were also tested to choose the most promising film. DBP was proved to be the most suitable plasticizer with a best using amount of 20%, such polymer films had low vapor transmission rate and low moisture absorption which were very important to an enteric coating material. The polymers was further characterized for film coating by evaluating the release of erythromycin tablets in vitro, hydrolyzed styrene maleic anhydride copolymer had lower water resistance in buffer solution of pH=1 which would result in destroy of the instable drug in acitic aqueous. Tablets coated with SMA-ethanol can satisfy the drug release requests of USP when the film weight gains were between 4-6%; tablets coated with both a subcoat and the polymer showed excellent gastro-resistance, less than 0.2% drug release occurred even with weight gains as less as 2% after 2h exposure to acid(pH=1), while over 90% drug release occurred in pH=6.8 sodium phosphate buffer within 45min, regardless of weight gains of coating material, moreover, we confirmed that the application of a subcoat could decrease the amount of required coating polymer. In conclusion, the potential use of SMA-ethanol as enteric coating material was demonstrated.