Abstract: In order to reduce the amount of slime water,the particle size of slime in the primary settlingtank,regulating tank and clarifier were analyzed,and the effects of microfiltration mesh,C -PAMaddition and pressure filtration time on coal slime water dehydration were studied. The results showedthat the average particle sizes of slime in the primary settling tank,regulating tank and clarifier were145.1 μm,103.2 μm and 91.9 μm,respectively. There were particles larger than 830 μm in theprimary sedimentation tank and regulating tank. The maximum particle size was larger than 1 200 μm.More than 20% of the particles in the three tanks had a particle size less than 45 μm. The 20 mesh mi-crofiltration and 15 mg /L C-PAM could effectively remove the particulate greater than 830 μm and lessthan 45 μm,respectively. The two methods together could improve the solid content of mud cake. Whenthe influent suspended solids were less than 3 000 mg /L,the pressure filtration time of slime water inthe high-efficiency rapid diaphragm filter press should be more than 40 min. When the influent suspen-ded solids exceeded 5 000 mg /L,the pressure filtration time should be more than 30 min. After treatedby the process of microfiltration + mechanical concentration + diaphragm pressure filtration,the solidcontent of slime cake was more than 70%,and the emission reduction of slime water reached morethan 90%. Close-