Dust generation behavior during BOF operation with minimal slag was investigated by measuring the dust concentration of the dust collecting water, and a dust generation model was proposed. In this model, the dust generation rate was expressed as a function of the carbon content in metal and the dynamic pressure at a metal surface of the oxygen top blown jet. As a result of controlling the dynamic pressure with the model, the dust generation rate during BOF operation was restrained and the oxygen blowing rate was increased by 10% to raise the productivity while maintaining the same rate of dust generation. To obtain data on the dust generation rate and clarify the behavior of the top blown jet, a new online system for measuring the dust generation rate for BOF was developed. The system enabled online continuous measurement of the dust generation rate by diluting the dust collecting water and using a colorimetric method to measure the dust concentration of the diluted dust collecting water. Application of the numerical simulation method to supersonic jets was considered and the behavior of the top blown jet was grasped in order to control the dynamic pressure. These tools were used to optimize the operating conditions and quickly evaluate the top blowing lance design under the Zero-Slag-Process.