Abstract: According to the problem of high content of clay minerals in raw coal in Wangfenggang coal preparation plant,the particle size distribution in range of less than 0.045 mm size fraction and the type and content of clay minerals in coal slurry was analyzed by laser particle size analyzer and XRE test,also the reagent optimization test for slime water was done to explore the effect of interval of reagent addition time between coagulant and flocculants on their cooperation effects.