Abstract: The effect of the fine coal fractions on the flotation of the coarse fractions was studied by the laboratory experiments and theoretical analysis. The results showed that the coarse fractions exhibited a fairly high flotation recovery while showed a sharply decrease by 65.69% in the presence of the fine fractions, however, the kaolinite has none effect on that. The concentrate yield rose up with the increasing collectors, however, it kept steady ultimately. The concentrate yield of the coarse fraction increased by 18.86% with an addition of 2500g/t sodium hexametaphosphate due to the reduction of interaction force between the coarse coal and fine coal particles caused by the sodium hexametaphosphate. Fine coal particles were mainly constituted by coal and mineral impurities associated body with both hydrophilic and hydrophobic surfaces. The extended DLVO theory analysis showed that slime coating can reduce the hydrophobic surface area and inhibit the flotation of the coarse coal.