Abstract: According to the problems of difficult-to-treatment acidic coal slurry water and serious corrosion of equipment in Kaichuan coal preparation,by adjusting the pH value of coal slurry,using different type of flocculent and agent which combined of coagulating agent and flocculent,researched the settlement characteristics of the coal slurry. The result showed that the potential value Zeta of coal slurry decreased with the increase of pH value,adding certain amount of NaOH making the pH value up to 7. With the using of flocculent TDX1412,the settling rate increased and don’t plug the pipeline,the absorbance of clear water is small,which reached the higher level of closed cycle of washing water,meanwhile,it also the reduced corrosive of slurry to the pipeline,so lower the production cost.