Abstract: In order to explore the factors leading to the high moisture of flotation concentrate and tackle the difficult problems in dewatering of such coal, an analysis is made of the property of the coal together with an experimental study of the effect on dewatering of the coal produced by the use of different hydrophobic modifiers.Test results show that the high moisture of total clean slime and flotation concentrate is attributable to the high content of micro and ultrafine particles and the presence of hydrophilic clay minerals in flotation concentrate; the use of hydrophobic modifiers can lead to drastic reduction of moisture of clean coal; in terms of dewatering effects that can be obtained with the use of the three modifiers, the palmityl trimethyl ammonium chloride(1631) ranks first followed by amino dodecane(DDA) and dodecyl trimethyl ammonium chloride(1231); the use of 1631 at a dosage of 150 g/t can lead to effective reduction of moisture of coarse slime; and for the dewatering of flotation concentrate, a best result can be obtained with the use of 1631 and 1231 at a respective dosage of 150 g/t.As evidenced by verification test, the modifier 1631 can maintain a stable effect and a best result can be expected when it is used at a dosage of 150 g/t.