Abstract: GB/T 35052—2018 is a national standard which is formulated for the first time according to the current development of heavy medium coal separation technologies both at home and abroad. Following a detailed account of the necessity and significance of the formulation of the standard as well as the measuring procedures and the standard implementation example, the paper underlines the focal technical point of the standard, i. e. the definition of the upper limit of size of magnetic material in heavy medium suspension.