Abstract: In order to study the mechanism of surfactants promoting dewatering of flotation clean coal,taking the difficult-to-dehydrate flotation clean coal as the research object,the flotation clean coal slurry was modified by sodium dodecyl sulfate (SDS),dodecyltrimethylammonium bromide (DTAB) and lauryl polyoxyethylene ether (Brij35),and the dehydration test was carried out.The results showed that:DTAB had the best filtration effect,and the moisture content of the filter cake decreased by 7.67% under the optimal dosage; the SDS filtration effect was the second in the selected surfactants.The moisture content of the filtration cake decreased by 6.61% under the optimal dosage; while the Brij35 had the worst filtation effect,the moisture content of the filter cake was only decreased by 3.94% under the optimal dosage.The properties of coal surface and reacted with different surfactants were characterized by contact angle measuring instrument and X-ray photoelectron spectroscopy.The results show that all three surfactants can improve the hydrophilicity of coal surface to some extent.The surface tension of the filtrate after the reaction of the three surfactant was measured by a surface tension tester.The results show that the surfactant can greatly reduce the surface tension of the filtrate,especially the surface tension of the filtrate after the reaction of DTAB is only half of that without the reaction of the reagent.The reduction can promote the removal of capillary water between coal particles,which is the major reason for reducing the moisture of flotation clean coal cake.