Abstract: Bubble size distribution during ladle bottom argon-blowing directly affects the refining performance. A hybrid VOF-DPM numerical model coupled with bubble collision and coalescence models is established to systematically describe the dynamics of slag-metal interface as well as the motion and evolution behaviours of numerous discrete bubbles. The accuracy of the model is validated by water-model experiments. Further, systematic simulation and analysis are performed to investigate the influences of three key process parameters, namely bottom-blowing flow rate, blowing position and double-hole included angle, on bubble size distribution and slag eye morphology for a 120 t ladle. The results show that bubble coalescence and slag-eye expansion are significantly promoted with the increase of bottom-blowing flow rate. When the flow rate rises from 80 to 400 L/min, the average bubble diameter is increased by 30.1%. The flow-field structure can be optimised by varying the bottom-blowing position. As the bottom-blowing position is shifted from 0.1r(r denotes the ladle bottom radius) to 0.7r, the average bubble diameter is first reduced by 16.4% and then increased by 14.3%, and the slag-eye area is decreased first and increased afterwards. Finer and more dispersed bubble groups are obtained near 0.3r. The interaction between two bubble plumes can be regulated by adjusting the double-hole included angle. As the double-hole included angle increases from 45° to 180°, the average bubble diameter is first reduced by 9.8% and then increased by 7.8%, the slag-eye area decreases first and increases subsequently, and more remarkable variations of bubble size are observed at the ladle top.