Abstract: In order to solve the problem of large amount and poor dispersibility of traditional collectors such as kerosene and diesel in the process of coal slime flotation, the diesel micro-emulsion collector was prepared using cetyl trimethyl ammonium bromide (CTAB), n-amyl alcohol or n-butanol, diesel oil and water as raw materials. CTAB was combined with n-amyl alcohol or n-butanol to form a complex emulsifier. The pseudo-ternary phase diagram showed that n-amyl alcohol was the best co-surfactant in the diesel micro-emulsion system. The micro-emulsion collector (MD) was prepared with a ratio of emulsifier∶diesel oil∶water as 22.62∶66.71∶10.67. The average particle size of oil droplets was 17.56 nm. The particle size of the microemulsion remains essentially unchanged after centrifugation. The average particle size of MD dispersed in water was 112.4 nm, which was much smaller than 123.88 μm of diesel oil. At the same collector dosage, the micro-emulsion significantly increases the concentrate yield, decreases the ash content, and improves the flotation perfection index. To achieve a concentrate yield of 79.45%, the dosage of the MD micro-emulsion collector was 135 g/t lower than that of diesel oil, representing a 45% reduction in collector consumption. Consequently, the flotation collector cost was reduced by 0.44 yuan per ton of dry coal slime. The contact angle tests show that MD can significantly enhance the hydrophobicity of coal particle surfaces, improve their floatability, and consequently increase the combustible matter recovery rate.