Based on the bench-scale opposed multi-burner (OMB) impinging entrained-flow gasifier and advanced visualization apparatus, studies on the coal water slurry (CWS) atomization process in gasifier were carried out. Morphological classification of the CWS atomization was discussed in detail. The particle size distribution of CWS after atomization was obtained by image processing algorithm and statistical method. The primary atomization modes in gasifier can be divided into: Rayleigh-type breakup and superpulsating breakup. Besides, the spray angle and breakup length are negatively correlated with the oxygen-CWS relative velocity. The secondary atomization modes can be divided into: no breakup, tensile breakup, shear breakup and synergistic breakup. The statistical analysis shows that the particle size of the CWS after atomization show a negative correlation with the oxygen-CWS relative velocity. The greater the difference in relative velocity between oxygen and CWS, the better the atomization effect, but excessive oxygen velocity results in reduced gasification efficiency. (C) 2019 Elsevier Ltd. All rights reserved.