"GB/T 11107-2018" is a national standard for the determination of the specific surface area of powders of metals and their compounds and the estimation of the average particle size. It specifies the principle, instrument, test procedure and result calculation method using the air transmission method. This method calculates the specific surface area of the powder by measuring the pressure drop of air flowing through the powder bed at a specific Flow velocity, based on the Kozeni-Karman theory, and indirectly deduces the average particle size related to the specific surface area. This standard applies to the corresponding materials that can form stable and breathable powder beds in drying and compression states, and provides a common test method for production control and mass inspection in powder metallurgy, New materials and other industrial fields.