Abstract: To address the problems of high slime yield (approximately 18%), high ash content (approximately 35%), a large proportion of fine particles (over 70%), and poor floatability of anthracite slime at Lutaishan Coal Preparation Plant, which restrict normal plant operation and result in coal resource losses, a “thickening flotation + surface modification conditioning”process was adopted. A BCF-type variable-frequency aerated mechanical agitation flotation machine was selected as the key flotation equipment. The intrinsic mechanisms responsible for the poor floatability of the high-ash fine slime anthracite were systematically investigated, and the flotation process parameters were optimized. An industrial-scale flotation test was conducted on the full size fraction (< 0.75 mm) of high-ash fine slime anthracite. The results show that the proposed flotation process can effectively improve the floatability of high-ash fine slime anthracite and achieve efficient separation of coal slime. The ash content of the flotation clean coal was reduced to ≤11%, while the ash content of tailings exceeded 70%. The clean coal yield reached 63.17%. Compared with direct sales of coal slime, the process generated additional economic benefits of 28.1887 million yuan per year. This study not only resolves the problem of slime accumulation at Lutaishan Coal Preparation Plant but also provides a reliable technical reference for the flotation of similar high-ash fine slime anthracite. It is of great significance for improving coal quality, enhancing economic efficiency, and promoting green development in the coal industry.