Abstract: The knotty problems in flotation of oxidized coal include low flotation efficiency, low yield and high ash of concentrate, and high consumption of agents, among others. To address this issue, a novel collector KD, a compound collector composed of mixed diesel and polar agent, is used and the feed concentration as well as the agent usage regime, such as dosages of collector and frother, and ratio of polar agent and diesel are optimized in the flotation process of the difficult-to-float coal. Besides, experimental study is conducted on the efficiency that can be expected in flotation of the coal with the use of KD at a ration of polar agent, and a proper dosage of frother. As revealed by study results, the adsorptive capacity of the polar-nonpolar compound collector on coal surface is far higher than diesel, and its adsorption can lead to increase of contact angle and hence increase of hydrophobicity of coal surface; and with the use of the compound collector, the flotation efficiency of oxidized coal is significantly improved as evidenced by a high yield of concentrate of 75.05%, a concentrate ash as low as 8.33%, a flotation perfect index of 50.89% and a recovery of combustible matter reaching 84.52% — a result attesting to significantly improved efficiency in flotation of such coal with the use of the compound collector.