GB/T 13390-2008 is a national standard for metal powders. It specifies a detailed method for measuring their specific surface area using nitrogen adsorption method (usually based on BET theory). The standard specifies the principle of nitrogen adsorption method, required equipment, sample pretreatment, specific measurement steps, calculation method of results and format requirements for test reports. Its purpose is to provide an accurate and standardized specific surface area measurement scheme for the scientific research, production and application of metal powders, which is suitable for powder metallurgy, additive manufacturing and New material development.