A new method was proposed to assess the surface properties of coal hy adsorption of metanil yellow using a continuous feed sg stem. The area fraction of the hydrophobic site on the exterior surface, alpha(m), was measured for Datong, Tyanfu, Shanxi No. 1, Illinois No. 6 and Blair Athol. Except for Tyanfu coal, the order of the values of alpha(m) is consistent with that of carbonaceous materials recovery. The,metanil yellow adsorption experiment requires no specific preparation, and can be applied to powder samples.