Abstract: Taking example of difficult floated coal slime from coal preparation plant of Pangpangta mime,based on float- and- sink test and timed- release analysis,it is difficult to float this slime as a result of high content of intermediate density material. Different results of slime flotation test are obtained at different degree of dissociation,however,the best floatation with the 74. 37% yield of clean coal and 9. 52%ash content of clean coal,is obtained in 7 minutes of grinding slime （average particle size to be 11. 75 μm）. Compared with original slime,yield of clean coal is increased by 6. 05%,and ash content of clean coal is reduced by 6. 08%.