The atomization and discharge characteristics of coal-water mixture(CWM) fuel at the internal-mixing type atomizer with one exit hole were investigated using Malvern droplet size analyzer which is based upon the laser diffraction method. Test results showed that over the atomizing pressure more than 2.0kgf/cm2, a critical flow phenomenon occurs, and that, consequently, a linearly proportional relationship is established between air mass velocity and absolute pressure in the mixing chamber, and further that the discharge coefficient of air is decreased with the increase of nozzle diameter and CWM mass velocity. The CWM droplet size in the range of 50-120㎛ MMD was sharply decreased with the increase of air/fuel ratio, but was maintained at a fixed value over a certain level, regardles of the CWM feed rate. On the other hand, its SMD was in proportion to the 0.48 power of the term, (1+fuel/air ratio). Also along with the axial distance from the atomizer, CWM droplet size was linearly increased and the obscuration was decreased. Since the MMD of CWM droplets is shown to be larger than that of coal particles in CWM fuel by more than about 20㎛, it was clearly verified that a CWM droplet consists of several coal particles and water, not just one coal particle.