Abstract: Hydrophbic modification is an effective approach for reducing moisture content of flotation concentrate and thus the moisture content of total clean coal product. Exploring the mechanism of action of hydrophbicity modifying agent is crucial for enhancement of hydrophobicity modification, reduction of moisture of flotation concentrate and selection of appropriate modifying agent. In order to explore the effect of hydrophobicity modification for aiding filer dewatering of flotation concentrate, the concentrate product from Suntun Coal Preparation Plant is taken as the object to conduct characterization analysis of mineral composition and surface property of flotation concentrate using up-to-date testing and analysis techniques, study of the effects on reduction of moisture of flotation concentrate produced by different hydroprobicity modifiers through suction filtration and centrifugal dewatering testing, and analysis of micromechanism of interaction between modifying agent and surface of concentrate through molecular dynamics simulation.Resultsof experimental study show that the considerably high moisture of concentrate is mainly attributable to the presence of clay minerals and hydrophilic mineral like quartz; with the use of hexadecyl trimethyl ammonium chloride(1631⁺) as hydrophobicity modifier, the moisture of concentrate can be noticeably reduced and maintain at a stable level; and with the use of the agent at a dosage of 100g/t, an optimum result can be expected, and the moisture of concentrate can see a drop by 1.62 percentage points. As revealed by molecular dynamics simulation, upon absorption of 1631⁺ on surface of concentrate particles, its carbon chain is twisted with the polar head facing the surface and the carbon chain facing the solution, making it possible to be uniformly distributed on particle surface and dispel partially surface bound water moleculars, thus beneficial to reduction of moisture of concentrate. The remarkable effect of 1631⁺ is well theoretically demonstrated by experimental dewatering results.