Abstract: In order to figure out the influence of surface roughness on the floatability of coal, a series of roughness coal pieces were prepared by using a grinding and polishing machine, and the contact angle measuring instrument and the adhesion measuring instrument were respectively used to test the change of contact angle,the induction time and the maximum adhesion force between coal and water droplets of the surface of the coal samples. Finally, the effect mechanism of roughness on the floatability of coal was explained by the Wenzel wetting model. The results show that as the surface roughness of the coal sample decreases, the surface contact angle will gradually increase. From the original sample to three different smooth coal samples, the contact angles are 64.2°,70.4°,77.0° and 91.7°.According to the Wenzel wetting model, the groove structure of the rough coal surface is filled with water, the actual contact area between water and coal increases, and the apparent contact angle decreases. The induction time and coal-water the maximum adhesion force gradually show a decreasing trend with the increase of roughness, indicating that the increase of surface roughness will reduce the floatability of coal. Rough coal particles are difficult to be captured by bubbles during flotation. For this reason, it is recommended to use high-intensity pulping equipment to treat the slime, reduce the surface roughness of the coal particles, enhance the floatability of the coal, and improve the flotation efficiency.