Abstract: The coal slurry water generated by Xiagou Coal Preparation Plant is difficult to settle, causing, as a result, the deterioration of the circulating water. To address the problem, the plant conducts a study on sedimentation characteristics of the slurry water with the addition of different kinds of flocculants and coagulants. Result of study shows that the slurry is difficult to settle in a natural manner, and the use anionic Al9020 flocculant in combination with proper dosage of polyaluminium ferric chloride (PAFC) can significantly improve the slurry settling rate; and the quality of circulating water can be greatly improved by apply the most optimum agent regime of first adding PAFC and then Al9020 at a dosage of 120 g/m³ and 24 g/m³respectively.