Objective To establish methods for detection of water in rubber closures as one of the Chinese Pharmacopoeia series of standards for pharmaceutical packaging material.Methods The formulation process of determination of water in rubber closures was explained,the key contents of the standard were analyzed,and the determination results of water content by oven-drying method and Karl Fischer drying furnace-coulometric titration method were compared.Results The determination results of water content in multiple batches of rubber stopper samples by over-drying method were generally higher than that by Karl Fischer drying oven-Coulometric titration method.The latter method is highly specific and accurate,and can better reflect the true water content of rubber closures.Conclusion Two methods for determining water content in rubber closures have been developed.Enterprises can choose the appropriate method based on the intended use of their products and daily testing needs.