A series of industrial experiments were conducted, not only to reveal the distribution and evolution of particle mass and size inside the flash converting furnace, but also to investigate the influence of airflows on the particle distribution. The results showed that the average size of particles grows 2-3 times when falling through the reaction shaft, and large aggregated particles were mainly distributed in the center and outer part of the material cone. This phenomenon was attributed to the collision and aggregation of molten particles caused by the high turbulent intensity of airflow, high particle mass concentration, and positions of natural gas combusting. Moreover, increasing the momentum ratio of the distribution air to the process air helped the particles to be distributed more uniformly, which could be beneficial to matte oxidation. Compared with changing process air, adjusting the distribution air could improve the particle spatial distribution more efficiently.