Coal water slurry (CWS) gasification technology, which is one of clean and efficient coal gasification approaches, catches wide attention presently. To investigate breakup and atomization of coal water slurry, eight kinds of CWS are observed using high speed digital camera. Based on morphology, the breakup regimes of CWS can be termed different modes: Rayleigh-type breakup, fiber-type breakup and atomization. The Rayleigh-type breakup is the main atomization regime of high viscosity CWS. When the viscosity of CWS is low, the CWS jet is Rayleigh-type breakup at low air velocity; and fiber-type breakup at high air velocity. When the air velocity is very high, all CWS jets are in atomization regime. The dimensionless CWS jet breakup length is studied and correlated, which decreases with Weber number and momentum flux ratio, increases with Ohnesorge number. Finally, a simplified formula is studied to estimate the oscillation frequency of CWS jet. The model estimates are consistent with the experimental results. (C) 2012 Elsevier Ltd. All rights reserved.