GB/T 6288-2021 "Method for the Determination of Particle Size of Granular Molecular Sieves" applies to the particle size determination of spherical and bar-shaped molecular sieves, specifying the test instruments, operational procedures, and data processing standards. For spherical molecular sieves, a standard test sieve with a diameter of 200mm (aperture 0.4mm–5.6mm) and a standard vibrating sieve machine are required, while for bar-shaped molecular sieves, a vernier caliper with an accuracy of 0.02mm is used. By weighing the sieve fractions after vibration or measuring the size of individual particles, the particle size distribution and average particle/bar diameter are calculated to ensure that the particle size indicators of the molecular sieves meet application requirements.