Abstract: The acid coal slime water of Wuhushan Coal Preparation Plant is taken as the object to investigate the property and mineral composition of the slime, and the natural sedimentation characteristics of the slime water. Meanwhile, study is conducted with aid of reagents to explore the influence on the sedimentation of the slime water produced by such factors as the kinds, dosages and proportions of agents used, and the pH value of water. As evidenced by test results, the slime water shows a low natural settling rate, making it difficult to achieve an effective settling result under natural settling condition; in the case of using agents as settling aids, the effect of conventional polyacrylamide(PAM) is greatly affected by the pH value of water, and its use can produce little effect in acid water; and the combined use of the new-type sodium polyacrylamide copolymer flocculant and diallyl dimethylammonium chloride coagulant at an optimum total dose of 184.67 g/t and a best ratio of the two agents can help optimize the slime settling condition and improve the sedimentation effect.