Abstract: An analysis is made of the problems encountered in operation of the density control system of Lyujiatuo Coal Preparation Plant's heavy medium separation process, which include irrational control mode, slowness in making medium density readjustment, low control accuracy, ageing of equipment, and inability to keep management of process control data.Based on analysis of the advantages and disadvantages of the 2 kinds of density meters in current use, the plant's heavy medium cyclone system is selected of making comparative industrial test.Through step-by-step optimization of the medium density control mode in line with the coal property and operating conditions of equipment, the qualified rate and yield of clean coal is significantly increased and the archiving management of control data is realized, making it possible for the plant to enhance its technical and management levels.