Abstract: Coal slime content and ash content is high in Wangjiazhai Coal Preparation Plant, in -0.5 mm graded coal slime mixed flotation process, it often appeared coarse or fine mud entrainment phenomenon. In order to fully recover combustible materials in the coal slime, the properties of coal slime in this plant were analyzed by slime sieving test, float and sink test and step release test, and three flotation processes of coal slime mixed flotation, classification flotation and secondary flotation were tested and studied by orthogonal experimental design method. The results show that the secondary flotation process is the most suitable for coal slime flotation in the plant, which can effectively reduce influence of high ash fine slime on cleaned coal and the ash content of the flotation cleaned coal. The optimum flotation conditions of the plant are coal slime concentration of 80 g/L, kerosene consumption of 240 g/t and No.2 oil consumption of 120 g/t, improved flotation index of 45.63, flotation cleaned coal yield of 69.93%, ash content of 11.88%, the primary and secondary relationship of each factor is No.2 oil consumption > coal slime flotation concentration > kerosene consumption.