Abstract: Qianjiaying Coking Coal Preparation Plant produces each year a large amount of middling product, causing therefore a substantial waste of coal resources. To tackle this problem, test is conducted on the flotation of the plant's middling product of flotation circuit using the new-type H70 series agents ( collector—H707, frother—H708), and the effect of flotation is compared with that obtained by using the original agents ( collector—diesel and frother—fusel) . Test result shows that when the two kinds of agents are used with the same dosage, use of the H70 series agents can lead to an increase of yield of concentrate, and ash of tailings and combustible matters, which are 10 percentage points, 5 ～ 8 percentage points and 8 ～ 10 percentage points higher respectively than those when the former agents are used.