Abstract: With the increasing degree of mechanized mining, the proportion of ultrafine particles in raw coal has risen significantly, resulting in an increasingly prominent slime coating phenomenon that severely constrains clean coal recovery and product quality. This paper systematically reviews the mechanisms, characterization methods, and mitigation strategies of slime coating in coal flotation. The mechanism of slime coating primarily involves the attachment of fine slime particles, such as clay minerals, onto coal particle surfaces through interactions including electrostatic double-layer forces, van der Waals forces, and hydrogen bonding, forming a slime coating layer that induces surface hydrophilization of coal. This process is strongly influenced by factors such as mechanical energy input, particle shape and surface roughness, slurry pH, and electrolyte conditions. Characterization methods are classified into indirect and direct approaches. Indirect methods, including micro flotation tests, induction time measurements, contact angle analysis, zeta potential distribution, rheological measurements, and sedimentation tests, are employed to evaluate the effects of slime coating on coal floatability and surface hydrophobicity. Direct methods, such as scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS), atomic force microscopy (AFM), quartz crystal microbalance with dissipation monitoring (QCM-D), particle size distribution analysis, and mineral slime coating test systems, enable quantitative assessment of the extent of slime coating. Regarding mitigation strategies, physical methods—such as pre-desliming, high-intensity conditioning, and ultrasonic treatment—suppress slime coating by separating or disrupting the slime coating layer, whereas chemical methods, including the addition of dispersants, pH regulators, and depressants, alleviate slime coating by regulating interfacial charge characteristics and steric hindrance effects. By introducing an integrated analytical framework of “mechanism-characterization–mitigation strategy–process selection”, this paper strengthens the linkage between fundamental understanding and engineering application of slime coating control. Furthermore, future research directions are discussed, including multi-factor coupled mechanistic analysis, in situ and dynamic characterization techniques, and the development of green and efficient mitigation processes, aiming to provide systematic guidance for the optimization of coal flotation and the efficient separation of fine coal slimes.