Abstract: For enabling the washery to produce quality consistent products with comparatively low medium consumption,the heavy medium density control system is turned into an automated one through technical upgrading carried out according to the characteristics peculiar to the plant.After the application of the upgraded control system,a quality consistant clean coal product with a higher yield can be obtained,thanks to the possibility of effecting automatic control of medium density and automatic adjustment of process parameters.This not only provides a technical basis for the plant to realize high-output,high-efficiency operation and modern management,but also brings considerable economic benefit.