Abstract: the paper analyzed the situation of settling of coal slurry in coal preparation plant of Linxi mining company of Kailuan group Co.,Ltd.Take the measures of optimization selectig the flocculant and coagulant,choosing the regime of agent,improving the agent adding method as well as separating and treating the floater floated on the water surface of rake thickener,which effectively solved the problem of circulating water pollution caused by the oily flocculate that existed in fine slime Linxin coal preparation plant and ultrafine particle in No.8 coal seam in Linxi colliery,so ensured the quality of production water.