Abstract: For the purpose of studying the properties of large droplets(d>50 μm) in the bag breakup regime and the unique harmfulness of large droplets breakup in aircraft icing process, the VOF method has been introduced to track the gas-liquid interfaces of droplets at different Weber numbers(16-22). The simulation has been conducted with Ohnesorge number of 0.00473 and Reynold numbers of 1662-1948. In this work, the typical deformation and fragmentation processes of large droplets in the bag breakup regime have been observed, and the processes are divided into 5 phases. Furthermore, the morphological characteristics have been analyzed with Rayleigh-Taylor instability and Rayleigh-Plateau instability. In addition, the calculation has been performed regarding the parent drop cross-stream diameter, the drop breakup time, and the drag coefficient. The validation has been carried out for the dimensionless functions representing the relation between breakup time, drop cross-stream diameter, and drag coefficient. The simulation results are in good agreement with the experimental observations and the results of the bag-type breakup theoretical model (BTB theoretical model). It is showed that the VOF method is effective to capture the breakup properties and can be applied in further studying the mechanism of drop atomization.