Abstract: The influence of variation of property of feed coal on flip-flop screen′s screening efficiency, and both oversize and undersize fraction is investigated by varying surface moisture and content of fine material of feed coal. Study result shows when the surface moisture is controlled at around 7%, the screening efficiency reaches 75% which can go up to 90% with the proportion of fine material being at 50%, demonstrating the high capacity of the screen in treating difficult-to-screen coal. The study may serve as a reference for coal preparation plants to improve wet fine coal treatment process and make design and selection of such parameters as size of opening and percentage open area of screenplate of flip-flop screen.