Abstract: The high-step throwing and blasting operation of open-pit mines will instantly release a large amount of high-concentration dust, seriously threatening the health of the operators and destroying the regional atmospheric environment, becoming a restrictive factor in the construction of green mines. Taking the high-step throwing blasting dust at an open-pit mine as the research object, through on-site monitoring and sampling experiments, the dust concentration timing data and particle size distribution rules were obtained. Based on this, a three-dimensional geometric model of throwing blasting dust migration was established, and the dust migration transient simulation was performed using fluent, revealing the migration rules and settlement mechanism of throwing blasting dust at different stages, and comparing and verifying them with the measured data. The results show that the diffusion of thrown blast dust can be divided into three stages: impact movement, mushroom cloud formation and diffusion movement; the particle size of thrown blast dust is mainly medium-fine particles, and the respiratory dust of <10μm accounts for 10%, and the dust of <50μm exceeds 50%. Numerical simulation clearly reproduces the dust migration evolution process: initially high concentration ejection, mushroom clouds are formed through buoyancy and wind field, and transported to the downwind, and finally gradually diluted. Different particle sizes showed significant divisions: coarse particles (>100μm) settled rapidly, medium particles (20–100μm) were transported with the wind, and fine particles (<20μm) were suspended for a long time and spread from a long distance. The simulation and measured concentration have a high degree of timing agreement (relative average absolute error MAPE ≈13.2%), which verified the reliability of the conclusion. It provides a scientific basis for the source control and hierarchical prevention and control of thrown blasting dust.