Abstract: Aiming at a certain coal slime in Guizhou, the yield rate of -0.074mm class is 54.19%, the ash content is 40.55%, the yield rate of -0.045 mm class is 40.38%, the ash content is 40.79%, and contains a lot of pearl clay, Clay minerals such as kaolinite and double kaolinite, difficlut floated and high-ash coal slime that are easy sliming. The optimal flotation conditions of -0.5+0.25 mm, -0.25+0.074 mm and -0.074 mm classes (slurry concentration, collector dosage, frother dosage and mixing speed)were confirmed by the method of classification flotation. The optimal flotation conditions of -0.5+0.25 mm, -0.25+0.074 mm and -0.074 mm classes were compared with the whole flotation of -0.5mm class. The results show that the optimal dosage of reagents and process parameters for each size classes are different. Under the optimal flotation conditions, the yield of clean coal of classification flotation is higher than that of the full size flotation, and the ash content is lower than that of the full size flotation. The yield of tailings is lower than that of the full size flotation, and the ash content is higher than that of the full size flotation. That is, the flotation of the classification flotation is significant for the slime.