Breakage could promote liberation of minerals and make recovery of coal with low ash content possible by flotation technology. In the research presented in this paper, middling coal was ground by wet-milling with different media, namely wet-milling iron ball (WMIB) and wet-milling zirconia ceramics (WMZC). As the size-reduction of middling coal is a physical process, Fourier transform infrared spectroscopy (FTIR) analyses of ground products indicate no difference in organic functional groups. Exposure of mineral and cover of hydrolysis reaction products of iron ion on the generated surface of products of WMIB increase the hydrophilicity and worsen the flotation selectivity when compared with products of WMZC. Float-sink tests show that ground products of WMIB have a relatively higher cumulative yield at low density. However, the ash content of flotation concentrate in each size fraction of WMIB is higher than that of WMZC, which is mainly caused by the decrease of hydrophobicity and worse floating selectivity of coal ground by WMIB. Combustible matter recovery (CR) shows an increase with the decrease of particle size, but CR in flotation concentrating on each sized products is similar to products ground by different media.