Coal water slurry (CWS) requires a certain fineness and a reasonable particle size distribution by grinding, and the packing density has an important influence on the slurryability of coal samples. Under laboratory conditions, the dry grinding effect of ball mill, rod mill and planetary ball mill on a long-flame coal was studied, and then five groups of grinding products were selected for pulping to analyze influence of packing density on slurryability. The results showed that the gradation was beneficial to improve the slurryability of long-flame coal. The concentration with fixed viscosity of CWS increased linearly with the increase of packing density within a certain range, and when the packing density was 87.44%, the concentration with fixed viscosity could reach 61.48%. The long-flame coal CWS had good stability, and the water separation rate decreased with the increase of packing density.