Abstract: The hydrocyclone currently used by the plant is working with the trouble of having finer slime particles in its underflow and coarser particles in its overflow. To address this issue, the characteristic size distribution of both overflow and underflow of the cyclone, and the working principle of the cyclone and sieve bend are analyzed. Based on the result of analysis, and through changing the working conditions, tapping the potentials and bringing into full play the respective superiorities of equipment, the coarser slime particles control process is optimized. With the use of the optimized process, the coal slime can be effectively recovered. Practice shows the combined use of hydrocyclone and sieve bend under optimized working conditions can lead to effective trapping of coarser slime particles, elimination of presence of finer size in underflow and coarser size in overflow, and reduction of output of coal slime.