Abstract: In sewage treatment with coagulation and sedimentation method, it is difficult for lighter and finer particles to get separated. What's more, the equipment occupies a large floor space and operates with a high energy consumption. It is, therefore, proposed to switch to the use of the conical-disk cyclone clarifier. Inside the clarifier, a number of cone-shaped discs are fitted for obtaining a larger settling area and a higher settling rate of flocs. As evidenced by comparative test, the addition of the cone-shaped discs can effectively improve the separating performance of the clarifier. The law governing the effect on the performance of clarifier produced by variation of its structural parameters is investigated through performance test. Test result shows that the height of the cylindrical part and the insertion depth of and spacing between discs exert a significant bearing on the performance of the clarifier. With the use of the clarifier for treating coal slurry water having a content of suspended solids of 450 g/L, a turbidity of 125 NTU, a height of its cylindrical part of 600 mm, an insertion depth of disc of 400 mm, a spacing of 20 mm between discs and an overflow orifice diameter of 40 mm, up to 93 percent of solid particles can be separated out with a reduction of turbidity by 70.2%.