Computational fluid dynamics is an efficient numerical approach for spray atomization study, but it is challenging to accurately capture the gas-liquid interface. In this work, an accurate conservative level set method is introduced to accurately track the gas-liquid interfaces in liquid atomization. To validate the capability of this method, binary drop collision and drop impacting on liquid film are investigated. The results are in good agreement with experiment observations. In addition, primary atomization (swirling sheet atomization) is studied using this method. To the swirling sheet atomization, it is found that Rayleigh-Taylor instability in the azimuthal direction causes the primary breakup of liquid sheet and complex vortex structures are clustered around the rim of the liquid sheet. The effects of central gas velocity and liquid-gas density ratio on atomization are also investigated. This work lays a solid foundation for further studying the mechanism of spray atomization. (C) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.