Abstract: According to the hard and difficult treatment of slime cementation in Tian-hong coal preparation plant, this paper compares the traditional flocculating agent #1 and #2 with the new flocculating agent AL9020, and applies them to the settling test of slime water and analyzes its effect. Firstly, the slime was screened and X-ray diffracted, and the flocculating agent AL9020 was analyzed by infrared spectroscopy. On this basis, laboratory flocculating agent settling test and industrial flocculating agent settling test were carried out for slurry water, and the mechanism of the influence of three flocculants on the settling characteristics of slurry water was discussed. The results show that the slurry water has fine granularity and high clay mineral content. It belongs to typical high-sliming refractory slurry water. AL9020 has the best settling effect. The height of clarification zone is 18.4 cm and the transmittance of supernatant is 73.2% after 6 minutes in laboratory test. When the dosage is 14g/t, the concentration of overflow water is 1.5g/l.