Abstract: In order to tackle the problems encountered in the plant’s coal slime treatment system and other problems arising from there,an analysis is made of the existing operation condition of the plant and based on which a coarse slime separation system and an automatic reagent dosing device are added. Through technical upgrading of the slime treatment system,apart from an effective separation of the coarse slime,there have been seen an increase of clean coal yield by 3 percentage points,a reduced consumption of dense medium per ton of raw coal treated（ ＞ 2 kg/t） and a decrease of concentration of circulating water from 105 g/L to around 10 g/L. Moreover,the cleaning system is made possible to operate normally with a capacity increasing from 0. 90 Mt/a to 1. 20 Mt/a,bringing about a favorable economic return for the plant.