Abstract: In order to solve the problem of high ash content in clean coal and low ash content in tailings in coal slime combined flotation in Xinxing coal preparation plant,take the slime as the study object,conducted the classified flotation test on slimes in different size fraction. The results showed that the Xinxing coal preparation plant can utilize classified flotation process, and the classifying size at 0. 125 mm,and the ＞ 0. 125 mm size fraction can be separated by the flotation machine,and the＜ 0. 125mm size fraction can be separated by the flotation column.