Abstract: To improve coarse clean coal slime with high ash and moisture caused by poor vibrating sieve bend in Kongzhang coal preparation plant,comparing coarse coal slime separation technology in form of technological process,system reliability,cost etc.,modification plan is determined. The application shows that the ash of coarse clean coal slime is decreased by 11. 92 percent,the percentage of clean coal carried in middlings is reduced by 18 percent,which gives rise to 3. 79 percent increase in yield of clean coal and to obtaining remarkable profits.