Abstract: Slime water treatment is a extremely important link in coal preparation process,its clarity directly affect the flotation effect,and adding the flocculant is an important means to improve the slime water clarity.According to the characteristics of slime water,using DLVO theory to analyze the flocculation mechanism,determine the intrinsic factors which influence the flocculation effect,on the basis of that,the flocculant is optimized to improve the flotation effect.