Abstract: The trouble with power coal preparation plants in slime water treatment is the difficulty to let the slime settle down. As the reagents in common use cannot yield the desired result, the plant have to resort to using imported reagents for accelerating slurry settlement. To revert this situation, the effect that can be obtained with the use of FeSO₄·7H₂O as an alternative to ordinary agents is investigated. Test results show that in comparison with the use of aluminium polychloride, a much better slime sedimentation result and improved quality of circulating water can be expected. Furthermore, FeSO₄·7H₂O is low in cost and free of chloride ions, and its use produces negligible effect on corrosion of coal washing equipment and structure of plant. It provides a new option for slurry water treatment.