Abstract: Under the role of the different crushing methods, due to the variation of the surface properties, the middlings would affect the status of the crushed coal f loatation behavior. Based on a phase composition analysis, the jaw crushing and wet iron medium ball milling method were individually applied to crush the middlings to - 0.5 mm. The experiment results of the middlings and the crushed products showed that the dissociation effect of the products crushed with the wet ball milling would be better than the products crushed with the jaw crushing. The X- ray photoelectron spectroscopy analysis showed that dissociation of the associated pyrite could detec t the pyrite and iron sulfide from the surface of the products crushed with the jaw crushing. An oxidative atmosphere of the wet iron medium ball milling could make the pyrite and iron sulfide on the surface of the coal particle turned to hydroxyl iron oxide. An infrared spectrum analysis showed that the wet iron medium ball milling could improve the water methyl group content on the coal particle surface and the content of the hydrophilic hydroxyl group would be reduced. The dissociation degree of diff erent crushed products and the differential of the surface property would make the floatation effect different. When a floated clean coal yield was 10%, an ash content 0 f the clean coal crushed with the wet ball milling would be 2. 14% lower than the ash content of the products crushed with the jaw crushing. The stage floatation results showed that except for the 0. 25 ~ 0.125 mm, the floatation effect of the products with0.5~ 0.25, 0.125 ~ 0.074 and- 0.074 mm crushed with wet ball milling would be all higher than the relevant particle products crushed with the jaw crushing.