The ISO 13320-2020 standard specifies the principles and methods for the determination of Particle size distribution using laser diffraction. The standard describes in detail the specification requirements for laser diffraction instrument operation, sample preparation, data collection and analysis, while providing guidance on the test environment, instrument calibrating, verification of results and uncertainty analysis. Laser diffraction is suitable for the analysis of particle size in the micrometer to millimeter range and is widely used in the fields of chemical, pharmaceutical, food, mineral and materials science. This standard aims to ensure the accuracy, conformity and repeatability of the test process, provide a scientific basis for the evaluation of particle properties, and is an important technical reference in the field of particle analysis.