Abstract: The national standard GB/T 35051—2018 《Grade of Coal Preparation Plant Closed Washwater Circuit》is a revised and renewed version of the Standard MT/T 810—1999—a previously formulated trade standard of the same title.In line with the current level of coal slurry water treatment technology and process equipment applied in both domestic and overseas coal preparation plants, as well as the specific conditions of China's representative plants, the grading indicators are redefined in the amended standard.The technical criteria for deciding on the grade of the said circuit of a plant include unit make-up water quantity, washwater concentration (percent of solids content), slime recovery, availability of buffer water facilities, and amount of raw coal treated a year (percentage of designed capacity).