Abstract: Buliangou coal slime is a long-flame coal, and its ash content, fine particle content and high-density content are high, and it is extremely difficult to separate by flotation. In order to achieve the effective separation of Buliangou coal slime, dodecane （non-polar agent）, amyl benzoate （ester polar agent）, and didodecyldimethylammonium bromide （DDAB, cationic Gemini surfactant） are used as collectors to investigate the selective effect of each reagent on Buliangou coal slime, and then the mechanism of action of the agent is analyzed by contact angle, FT-IR infrared spectroscopy, Zeta potential determination and quantum chemical calculation. The results show that when the above agents are used as collectors alone, the dodecane capture effect is poor, and amyl benzoate shows better capture and selectivity under high drug dosage, and DDAB has better capture, but the selectivity is poor. Based on DDAB, it is found that the flotation effect of Buliangou coal slime is effectively improved under the action of compound agent, and when DDAB is compounded with amyl benzoate, the recovery rate of refined coal combustible gas obtained by adding 2% DDAB reaches 83.63%, which effectively improved the flotation effect of Buliangou coal slime. Through the mechanism of action of the collectors, it is found that DDAB is first adsorbed on the surface of the slime through electrostatic action, which not only enhances the hydrophobicity of the surface of the slime, but also masks the hydrophilic sites on the surface of the slime, and strengthens the adsorption capacity of the follow-up agent on the coal surface, that is, it plays an activation role on the surface of the hydrophilic slime.