Based on coal flotation tail low ash content in Xiqu Coal Preparation Plant, the tail coal screening and fugitive dust experiment was carried out, the reason was analyzed. Through the analysis of the factors of classifying hydrocyclone classifier and coarse coal slime separation recycling process of optimization, adjusting the optimization of structural and operating parameters and grading hydrocyclone thick coal slime grading and separation process were put forward, which reasonably adjusted the coarse and fine coal slurry into the proportion of coarse coal slime separation and flotation system, reduced flotation into the material particle size limit and improved the flotation of coal ash.