Based on high content of fine silt of coal slime of raw coal, high ash content in roughing process of Dayuan Coal preparation Plant, in order to solve the problem, the coal quality analysis was conducted from particle size, density and flotability to floated coal slime, laboratory experimental study of desliming flotation scheme and the secondary flotation scheme were compared, the secondary flotation process of coal slime was put forward. The experiment result showed that the secondary flotation process could solve the problem of separation of extremely fine floated mine slime and its dehydration and improve the clean coal quality, clean coal rate was improved by 1.90%, more clean coal by 13 300 t per year, more economic benefit by 4 320 000 yuan, with obvious economic benefit.