Abstract: In order to tackle the problem regarding the settling and clarification of the slurry water containing highly degraded coal fines generated during coal washing process, natural sedimentation test is made with such slurry water of Shangwan Coal Preparation Plant as the targeted object, using both single and combined reagents. The effect of magnetic pretreatment on sedimentation and clarification of the slurry water is also investigated. As evidenced by test result, no effective settling of slurry can be expected through natural sedimentation process as indicated by the fact that after a period of 8 hours, the supernatant still exhibits a considerably high turbidity; the use of single flocculant or coagulant is unable to obtain the desired result; the combined use of the two kinds of agents can lead to a much improved result, but also brings about other problems including high consumption of agents, high treatment costs and environment related troubles. The magnetic pretreatment method proposed can help promote the fall of solids in water along with a much reduced turbidity of supernatant; and a best result can be observed by using the field-assisted method at a magnetic field intensity of 0.3 T and a magnetization time of 5 minutes.