To determine the effect of coal particle size on coal-water slurry (CWS) atomization, Sauter mean diameters (SMD) of spray droplets have been measured for various slurries containing three different coal particle sizes (32-45 mu m, 45-63 mu m, and 63-90 mu m). The test sprays are generated by a sonic air jet blasting onto the cross-injecting CWS mixture. The diffraction particle analyzing technique (the Malvern 2600D system) measures spray SMDs nonintrusively. The results show persistently that the spray droplet SMDs of the CWS containing smaller coal particles are larger than the SMDs of rite CWS containing larger coal particles, This finding is consistent with the fact that the former exhibits larger viscosity than the latter. In addition, the internal capillary holding force between the particles and water increases with decreasing particle sizes because of their smaller radii of curvature and larger total surface area, The increased holding forces of smaller coal particles enhance their resistance against the external airblast mid make the atomization difficult. However, smaller spray SMDs of the CWS containing larger coal particles are attributed to both their lower viscosity and their lower capillary holding forces, and thereby weaker resistance against the external airblast.