Abstract: The middlings and refuse slime water is treated in a mixed manner by the plant, which causes the downfall of the recovery of useful coal resource. To address the issue, the plant’s slime water treatment process is optimized based on analysis of the original coal washing system. Through technical upgrading, the middlings slime water and refuse slime water are separately treated in a classified manner, so as to realize secondary recovery of the combustible matters in the dilute medium of middlings. Practice shows that through separate treatment of middlings slime and refuse slime water. There has been seen a rise of yield of flotation concentrate from 10.84% to 11.71%, a decrease of yield of slime from 5.27% to 2.51% and an increase of slime ash up to 70.73%.