Abstract: Because of the low selectivity of diesel oil in flotation of ultrafine coal slime contained in the flotation feed, the concentrate product of the plant’s flotation system is high in ash, and the heavy medium separation system has to reduce the ash of its clean coal product to an unnecessarily low level. To address this issue, both bench-scale and industrial flotation tests are conducted by the plant to explore the feasibility of using the new-type MG-9^# collector for flotation of the ultrafine coal in place of the diesel oil. Practice shows that the use of the new collector has led to a drop of ash of flotation concentrate by 0.18 percentage point, an increase of ash of tailings by 4.08 percentage points, an upsurge of rate of stabilization of concentrate ash by 9.75 percentage points and a reduction of consumption of reagent by 16.79 percentage points, yielding a favorable social and economic result for the plant.